Page 1 of 34
Flues, chimneys and
combustion air
ventilators.
Technician’s guide to best practice Version 5 March 2020
Page 2 of 34
Flues chimneys & combustion air ventilators is published by the Cavity Insulation
Guarantee Agency (CIGA). It is one of a series of technician’s guides, intended to
contribute to best practice in cavity wall insulation.
Whilst every care has been taken in its preparation, CIGA and its authors specifically
exclude any liability for errors and omissions or otherwise arising from the contents of
this guide. Readers must understand the principles and practices described in relation to
any particular application and where necessary, take professional advice.
The information contained in this guide is not exhaustive. Further details on flues,
chimneys, and combustion air supply can be obtained from the following publications.
Gas Appliances
BS5440 – Flueing and Ventilation for Gas Appliances not exceeding 70kW
Part 1 2008: Specification for the Installation and maintenance provision for gas
appliances
Part 2 2009: Specification for the Installation of gas appliances to chimneys and
maintenance of chimneys
BS 5871 Specification for the installation and maintenance of gas fires, convector
heaters, fire/back boilers and decorative fuel effect appliances –
Part 4 2007: Independent gas-fired flueless fires, convector heaters and heating stoves of
nominal heat input not exceeding 6 kW (2nd and 3rd family gases).
Further Technical information should be sought / obtained from the relevant fuel
supplier;
Natural Gas
•
Gas Safe
Oil Appliances
•
(Oil Firing Technical Association for the Petroleum Industry: OFTEC) Solid
Solid Fuel
•
Solid Fuel Appliances The Building Regulations 2010 Part J Appendix F
www.planningportal.gov.uk
© . . .All rights reserved. No part of this publication may be reproduced, stored in a retrieval system
or transmitted in any form or by any means electronic, mechanical recording or otherwise without
the prior written permission of the copyright holder.
Page 3 of 34
LEGAL REQIREMENTS
The main legal requirements for protection of the public and
employees are the general provisions of Health and Safety at
Work act 1974, and related legislation, including the
Management of Health and Safety at Work Regulations 1999.
These require the drawing up of a ‘risk assessment’ plan of
protective measures, as well as the appointment of competent
persons to ensure that safety requirements are met effectively.
An example of a risk assessment for Flues, Chimneys and
Combustion Air Ventilators is given on page 32.
In addition, for gas installations, there is a requirement to comply
with the current edition of the Gas Safety (Installation and Use)
Regulations, and in particular: Regulation 8.
This covers alterations and modifications to buildings in
which gas appliances are installed and this would include
cavity wall insulation.
Page 4 of 34
PREFACE
“The Technician’s guide to best practice provides technicians
with a simple, but detailed manual. It covers best practice for
dealing with flues, chimneys and combustion air ventilators
during the installation of Cavity Wall Insulation (CWI). It clearly
sets out the responsibilities of the CWI installer companies,
with practical examples and illustrations of procedures to be
carried out by the competent technician.
The guide should be followed by all CWI installer companies
and used in conjunction with recommended training
programs.
Page 5 of 34
INTRODUCTION
This guide has been written for the CWI Company and technician, to ensure that the
performance of fossil fuel-burning appliances is not adversely affected by the installation of
Cavity Wall Insulation (CWI).
CWI should not be installed unless you can gain entry to the property, and you are able to
complete all of the necessary pre and post installation checks.
Installation is a relatively simple operation, but you must carry out your pre- and post-
installation checks correctly, or you put the occupants in real danger. If you block any
combustion air ventilators or flues of fuel-burning appliances, there is a high risk of
someone becoming seriously ill or dying of carbon monoxide poisoning.
All fuel-burning appliances need an adequate air supply and need a clear chimney /flue to
operate correctly and safely.
With an appliance in good working order the main products of complete combustion are
Carbon Dioxide and Water Vapor. Both of these gases are non-toxic, however if the air
supply becomes impaired or violated highly toxic carbon monoxide is produced. This is
known as incomplete combustion.
Where the products of combustion are unable to pass through a flue to outside
atmosphere, or they re-enter the premises through either a blocked or defective flue or
chimney it is referred to as ‘spillage’.
Carbon monoxide poisoning
You cannot see, smell or taste carbon monoxide, but it is an extremely toxic gas. It is
absorbed by the red blood cells via the lungs, resulting in illness or death. Exposure to high
levels of carbon monoxide can lead to death in as little as 1-3 minutes.
The symptoms of carbon monoxide poisoning can be confused with those of other
illnesses, such as colds and flu.
Someone exposed to the gas may complain of:
Unexplained headaches. Chest pains or muscular weakness, General lethargy or fatigue
Sickness, diarrhea or stomach pains, Sudden dizziness when standing up, convulsions
If carbon monoxide poisoning is suspected, all appliances must be switched off
immediately and not used again until the cause has been fully established and rectified.
Where carbon monoxide poisoning is confirmed the installation must not be disturbed
(other than making safe) and the incident reported to the HSE under RIDDOR.
Technician’s competence
To attain a level of competence, technicians must have successfully completed an
approved / registered Combustible Fuels Awareness training course covering all checks and
inspections referred to in this guide.
Page 6 of 34
CONTENTS
Title Page Title Page
• Legal Requirements 3 • Notes. 17
• Preface 4
• Combustion air vent
requirements solid mineral fuel
and wood burning appliances.
18
• Introduction 5
• Combustion Air Ventilation
Requirements for Gas Appliances
19
• Your responsibilities 7
• Combustion Air Ventilation for
Oil Fired Appliances
20
• Pre installation checks
• Carry out spillage test
• Installation checks
• Particular care
• Post – installation checks
8
• Ventilation requirements for
open flued – gas appliances.
21
• Advice to customers. 9 • Flues.
22 -23
24 -25
• Identifying appliance vents & flues 10 • Checking Flues & Appliances 26 - 27
•
Safeguarding the combustion air
supply
11 • Gas fired appliances. 28 - 29
• Common air brick types 12 • Gas safety notice. 30 -31
• Ventilation to suspended timber
floors
13
•
Risk Assessment relating to flues,
chimneys and combustion air
ventilators.
32
• Sub floor ventilation where
conservatories or extensions are
added
• Burnall Fires
14 -15 • Technicians safety checks. 33
• Combustion air ventilator
requirements
16
• Technicians safety check sheet –
flues, chimneys and combustion
air ventilators.
34
Page 7 of 34
YOU’RE RESPONIBILITIES
You must leave flues, chimneys and
combustion air ventilators in the same or in
better condition than before cavity wall
insulation took place.
When you identify that a fault could harm
the occupants or yourself, remember that
people’s health & well-being must be
safeguarded. You should take appropriate
action and or issue a Warning Notice.
You must ensure that the installation vehicle
is equipped with:
•
Smoke pellets and holder
•
Smoke matches and holder
•
Warning notices.
General.
The normal procedure of installing cavity wall
insulation should not affect the operation of
fuel – burning appliances, flues or chimneys.
The appropriate checks must be carried out at
all stages of the works:
•
Pre installation
•
Installation
•
Post installation.
When you leave the installation, make certain
that you have not blocked or compromised
any chimney, flue or combustion air
ventilators with insulation materials.
If for any reason a smoke / spillage test
cannot be carried out by the cavity wall
insulation installing technician, an approved
appliance maintenance contractor must carry
out the appropriate checks. (I.e. Gas Safe –
registered installer for gas appliances HETAS
or Solid Fuel approved engineer installer for
all solid fuel appliances – OFTEC registered
engineer for Oil appliances)
CARBON MONXIDE (CO) ALARMS
The Health & Safety Executive in
its discussion documents Gas
Safety Review: options for changes
states: HSE recommends the use
of CO alarms meeting all current
British Standards as a second line
of defence. It is emphasised by the
HSE that alarms must not be seen,
as a substitute for proper
regulatory installation
maintenance and safety checks on
Gas appliances and flues.
This view is endorsed by CIGA.
GLASS FRONTED FIRES
Some manufacturers state that
decorative canopies or fronts of
fires should be removed from gas
fires in order to carry out spillage
tests. Where these parts are to
be removed by the householder
and are not designed for the safe
use of the appliance, then this
can be carried out by the
installation technician.
Where removing the part would
affect the safe operation of the
appliance then this work must only
be carried out by a Gas Safe
registered installer.
Page 8 of 34
PRE- INSTALLATON CHECKS
Fuel burning appliances,
combustion air ventilators, and
the routes of all flues on
chimneys on external walls must
be located and identified.
Ventilators should be checked to
ensure that they are compliant
with the regulatory standards
and that chimneys are not
capped.
Appliances must be run, and the
flame observed, especially with
glass – fronted gas fires. Confirm
exit of combustion gases by
carrying out a flue, or spillage test.
Should any of the checks prove
unsatisfactory report them to your
supervisor and do not proceed
with the installation until the
problem(s) have been fully
resolved.
LOCATE and NOTE
•
Each Appliance Type:
o
Boiler
o
Space Heater (fire)
o
Other
•
Fuel Type Used
o
Gas
o
Oil
o
SmokelessOvoids
o
Briquettes, Wood,
o
Bio Fuel,
o
bituminous coal
•
Combustion air ventilators for each
appliance
o Location
o Type
o Compliant / None Compliant
CARRY OUT A SPILLAGE TEST’S WHERE
APPLICABLE
You must be satisfied that the ventilator’s
supplying combustion air for the fuel –
burning appliances meets the current
standards and requirements.
INSTALLATION CHECKS.
Installation procedures are fully detailed in
the Technicians Guide: Installing Cavity Wall
Insulation
PARTICULAR CARE IS NEEDED
DURING:
DRILLING.
When drilling holes, do not drill directly in
line with a chimney of flue.
INJECTION.
When installing cavity wall insulation near a
chimney or flue, check that no insulation
material is visible within the flue. Care and
attention should always be applied.
POST – INSTALLATION CHECKS.
Ensure that:
a) All combustion air ventilators
are clear and functioning
correctly
b) All flues on external walls are
clear and not compromised.
Go inside the property and
check for any visible evidence
of insulation material in or
around fuel-burning
appliances.
Ask the customer / occupant to
run each appliance then
Check the appearance of the
flame.
Page 9 of 34
For wood burners and
Solid Fuel Fires
you should observe flues and
chimneys from outside of the
property, to ensure that
combustion gases are being
exhausted.
Carry out Smoke / Spillage
tests for all fuel burning
appliances on external walls
and compare them with your
pre-installation safety checks.
You could be held personally
responsible and face prosecution
if occupants subsequently
become ill or die from carbon
monoxide poisoning due to
careless work on your part.
ADVICE TO CUSTOMER’S
.
If you are unsure about the
operation of an appliance or the
effectiveness of the flues,
chimneys and combustion air vents
you must issue a warning notice
(see pages 18/19) Explain to the
customer that the appliance must
not be used / operated until the
appliance and or its flueing system
has been thoroughly check by a
registered and approved
maintenance contractor.
Should you believe that a Gas
appliance is dangerous it must
be turned off and the Gas
Emergency Service or Gas Safe
registered contacted and
immediately notified.
For liquid petroleum gas –
Contact the Supplier.
The information provide here
does not cover every
eventuality.
IF YOU HAVE ANY DOUBT
SEEK TECHNICAL ADVICE.
Page 10 of 34
IDENTIFYING APPLIANCE, VENTS, &
FLUES
It is important to establish what fuel type is
used by each appliance. Different fuels and
appliances will have different flues, chimneys
and combustion air ventilation requirements.
Solid Fuel Fire
Flueless Gas Appliance
Always see these appliances in use before
Before installing cavity wall insulation to
compare its performance following the
installation
The flame pattern / colour should be noted at
pre and post installation checks
During the checks – look for staining, scorch
marks, in or around the appliance surround /
casings or other signs of distress as these may
indicate existing problems that must be
checked by a registered engineer.
Gas Appliance
Gas Fire Back Boiler
Coal Fire
Gas Appliance
Page 11 of 34
SAFEGUARDING THE COMBUSTION
AIR SUPPLY.
It is your responsibility to ensure that there
is the required level of combustion air
available to the appliances and for open
flues:
Initially you must locate, identify and note the
position of combustion air ventilators for all
fuel burning appliances within the property
and they are thoroughly checked
The combustion air supply to each appliance
or open flue must be isolated from the cavity
to guarantee an un-obstructed supply of air to
the appliance(s).
It is essential that each combustion air
ventilator is continuously sleeved across the
cavity (connected to both internal and
external ventilators).
In the event, that the combustion air supply
required for the appliance or flue has been
compromised, or has not been fitted, carbon
monoxide may be produced which could build
and cause serious illness to the occupants, in
severe cases there may be a fatality.
TYPICAL COMBUSTION AIR
VENTILATORS.
Combustion Air Supply Must Not Draw Air
from the Cavity Walls.
Combustion Air Ventilators
•
Must Not be Closable
•
Free from obstruction
•
Must not incorporate a mesh or fly
screen.
The fitting of or Existing Combustion
ventilators must comply with current
standards and stamped with -:
Free Area cm2 (i:e 100cm2)
Page 12 of 34
COMMON AIR BRICK TYPES
Due to the tapered design of their vent holes,
“Terracotta” air bricks only provide limited
free air flow and will not normally
Provide sufficient combustion air.
They must be replaced with a regulatory
combustion air vent.
Combustion air ventilators with fly screens
must be removed / replaced
Terracotta air ventilators are tapered and as a
result reduce air input
Terracotta Plastic Lovered
Lovered Vent Vent
OTHER VENTILATORS
Other ventilators include those
• providing under floor (to suspended
floors)
• Cavity wall & roof ventilators
• Room vents (kitchen / bathroom
• Extractor fans
• Air vents to larder / food storage.
All operational ventilators must be sleeved
and protected and maintained
(Kitchen / bathroom vents must be
maintained)
Bedroom ventilators must be maintained;
however, should the client request that these
are sealed over, record ventilator location and
its use on the work records.
Be careful not to confuse cavity vents with
others – such as under floor vents.
OBSOLETE CAVITY VENTILATOR'S.
These must be sealed with an appropriate
material to prevent
•
Material loss
•
water ingress
•
infestation
Maintaining air supply
•
Bedroom
Ventilator
•
Bathroom /
Kitchen
Ventilator’s
•
Under floor
Ventilators
•
Radon Gas
Ventilators
Concreted
Beamed
Floors
Page 13 of 34
Ventilation to suspended timber floor joists
External ventilators providing essential air
circulation to suspended timber joists and
floorboards must be identified and
safeguarded as necessary, as System Designer
and BBA specification.
Any reduction in air circulation to the floor
void following the installation of cavity wall
insulation due to unsafeguarded vents, would
rapidly raise humidity under the timber floor
and also within the property, increasing
condensation and ultimately providing an
environment entirely conducive for timber
destroying mould spores to develop.
Where vents are found to be compromised at
assessment stage due to debris, insects etc. a
thorough inspection of timber floors should
be undertaken to ensure there is no sign of
deterioration and if there is any doubt seek
further guidance.
Off-set external ventilation points for
suspended timber joists and floorboards may
not necessarily be directly above inner leaf
openings, and the assessment must therefore
confirm that under floor ventilation is not
compromised following the installation. This
may require the removal of an external vent
to visually confirm the inner leaf opening,
alternatively access below the timber floor for
confirmation will be necessary.
Where timber decking or raised garden
feature areas reduce the air circulation
pathway to the external vents a thorough
inspection must be undertaken to ensure all
vents are safeguarded.
If this cannot be confirmed due to
inaccessible areas the property may not be
suitable for the installation of cavity wall
insulation.
Page 14 of 34
Sub Floor Ventilation –
Conservatories and Extensions
Conservatories and extensions have become
extremely popular in recent years and the
constructions will generally include a concrete
and screed base.
Original pre-existing under floor ventilation points
will therefore be compromised, reducing air
circulation and cross flow ventilation within the
sub floor void. Extensions built to extend across
the entire rear elevation of a property also
compromises this essential cross flow ventilation,
raising humidity below the timber floor and
increasing the potential risk of timber destroying
mould growth to develop.
CIGA has seen a marked increase in recent years
of timber floo-board, and joist deterioration
caused by reduced cross flow ventilation, with
total collapse in some instances within two or
three years of the installation of cavity wall
insulation.
Positive and negative air pressure is essential, and
it is likely that conservatories and extensions will
reduce this essential air circulation below the
floor void, and this may in time cause similar
timber deterioration.
However, following the installation of cavity wall
insulation any subsequent deterioration will
inevitably be concluded, that if not totally caused
by the installation of cavity wall insulation, it
would certainly be considered to be a
contributory factor.
It is therefore essential that the assessment for
suitability for injected cavity wall insulation
considers the path for cross flow ventilation, thus
avoiding unnecessary risk of timber deterioration.
This may require the installation of additional
sized air vents on two sides of a property if
ventilation points on the rear elevation cannot be
replaced or introduced.
Burnall Fires.
Background
These types of appliance are predominantly found
in Northern Ireland but may have been installed
within other parts of the of the UK
When assessing buildings for suitability and the
type of heating is used, a robust inspection must
be carried out to confirm this this type of
appliance is applicable and noted within the work
records accompanied by photographic evidence.
This type of appliance requires combustion air
taken from either the ventilated sub floors of
buildings or via a piped ventilation to the outside
through the solid floors. substrate.
On this appliance type there is no requirement to
fit additional combustion air ventilation through
the external walls as this would impede the
operation of the appliance.
This appliance is also available with a back-boiler
system.
Instead of drawing air from the room, the Burnall
Fire relies on air supplied from under the floor to
burn its fuel. Air is to be supplied via underfloor
pipework fitted to the appliance. The method of
receiving the air flow depends upon the floor type
being Suspended or Solid Floors
.
Burnall Fires -: Cont’d
Page 15 of 34
How does the appliance work?
Obtaining a Draught for the fire.
•
When the floor is suspended There must
be a good flow of air under the floor to
prevent dry or wet rot. If there is a good
flow of air, the manufacturers of the
appliance recommend that a 2 foot
(60cm) length of air pipe is fitted to
project through the brick fender under
the hearth, making sure there is no
obstruction at the end of the pipe.
•
Inspect all the sub floor ventilators around
the house, to confirm that they all are
open and that a clear unobstructed air
flow is present.
•
Also check holes in all dividing walls and
walls that support the joists under the
floor.
•
if there is not a good circulation of air, it is
important to fit additional sleeved
ventilators directly to under floor air
space.
WHEN THE FLOOR IS SOLID:
•
These types of appliance are
predominantly found in Northern Ireland
but may have been installed within other
parts of the of the UK
•
When assessing buildings for suitability
and the type of heating is used, a robust
inspection must be carried out to confirm
this this type of appliance is applicable
and noted within the work records
accompanied by photographic evidence.
•
This type of appliance requires
combustion air taken from either the
ventilated sub floors of buildings or via a
piped ventilation to the outside through
the solid floors. substrate.
•
On this appliance type there is no
requirement to fit additional combustion
air ventilation through the external walls
as this would impede the operation of the
appliance.
•
This appliance is also available with a
back-boiler system. Instead of drawing air
from the room, the Burnall Fire relies on
air supplied from under the floor to burn
its fuel. Air is to be supplied via underfloor
pipework fitted to the appliance. The
method of receiving the air flow depends
upon the floor type being Suspended or
Solid Floors
Page 16 of 34
COMBUSTION AIR VENTILATION
REQUIREMENTS
Where a combustion air ventilator is
required. The ventilator must be fitted
before you proceed with cavity wall
insulation.
The nominal size and the free air area of
combustion air ventilators vary from
manufacturer to manufacturer. Dimensions
referred to in this guide are the nominal sizes
used by the trade, but the key consideration
is the free air cm2 area that the vent provides.
A number of different terms are used by air
vent manufacturers to describe the free air
area, including: ‘air flow rating,’ ‘free air
opening,’ ‘available air opening,’ and ‘vent
free area.’
Gas appliances must be provided with a
least 500mm
2
of free air per kW - above a
7kW net input rating.
Oil and solid fuel appliances require
550mm
2
of free air per kW - above a
5kW rating.
A table showing the vent free areas required
for any open flued gas appliance, up to a
70kW Nett rating is shown on page 21
OPEN FLUED – SOLID FUEL FIRES.
•
A permanent air ventilator must be fitted
in any room or space containing a
working solid fuel open fire. The only time
that a combustion air ventilator is not
required is when the fire has been
deemed out of service or redundant i:e
•
The fire basket has been permanently
removed. It is common practice for some
customers to wish to maintain the fire as
a decorative item with floral decorations
within them as a feature. It must be
stressed that unless the fire basket etc
has been permanently removed then the
fire requires a combustion air ventilator.
fitted.
•
You must Advise the customer that they
must not re- instate the fire unless a
registered and approved solid fuel
engineer has been contacted and
commissioned / appointed to test the
integrity of the flue and re-instate the fire
appliance
•
The Fireplace / flue opening is
permanently blocked / bricked up –
however caution must be taken to ensure
that the closed flue has a ventilator fitted
to the facing of the flue to reduce or
prevent condensation within the flue.
(see CIGA Technical Note : Redundant
Flues)
Always take digital evidence as
evidence and record details on the
work card
•
In the event, that the customer refuses to
have the required ventilator fitted, the
installation must not go ahead.
It is not acceptable for the customer to
provide the technician or installer
company with a letter saying that they
would take full responsibility for not
having the air vent fitted.
SOLID FUEL STOVES, CLOSED
APPLIANCES (Boilers / Cookers)
•
Approved document J
requires ventilation for any
appliance with a rated output
above 5kW or every kW
where the fire is fitted within
a property that has been
constructed since 2008
Page 17 of 34
Information regarding the input rating of a Gas Appliance can be found
on the appliance data badge.
Ventilation provided for Gas Appliances should not be oversized as this
can have a detrimental effect on the energy – efficiency of the
appliance. In turn this may encourage customers to block off the air
ventilator.
Note: For all Gas Appliances ventilation requirements are calculated from the
Net Values
Where the manufacturer specifies Gross values divide the Gross Value by 1.11
Where concern remains seek qualified advice.
Where the kW rating of the Gas Appliance cannot be determined, the Assessor
and technician must advise the customer that a combustion air ventilator must
be fitted.
Page 18 of 34
21
Combustion Air Ventilation Requirements for Solid Mineral
Fuel & Wood Burning Appliances.
Does the room contain a Solid Mineral Fuel or
Wood Burning Appliance?
Does the room contain a Closed appliance?
Approved document J requires:
• Ventilation for any appliance with or
without a draught stabilizer fitted?
• Ventilation required for any appliance for
every kW into a property built from 2008
Extract from -: Approved Document J Combustion Air Ventilation
Open Fire
The size of an air vent is subject to the throat area or cross - sectional
area of the flue-: [50%]
Closed Appliance
• Free air of 550mm2 x kW rating applies to appliances above 5kW
• Free air of 555mm2 x kW for homes built from 2008.
Table: ADJ Air Supply to Solid Fuel Appliances
Type of Appliance Type and Amount of Ventilation
Open appliance
Permanently open vent with a total equivalent area of at least 50% of
the cross-sectional area of the flue
Open appliance, such
as an open fire with a
throat.
Permanently open vent with a total equivalent area of at least 50% of
the throat opening area.
Open Appliance, such
as a stove, cooker or
boiler with a draught
stabiliser
Properties built before 2008:
• 300mm2/kW for the first 5kW of the appliance rated output
• 850mm2/kW for the balance of the rated output.
Equivalent area is measured -:
divide the area given in mm by 100 to find the corresponding area in cm2
Nominal fire size
(fireplace opening size)
350mm 400mm 450mm 500mm
Total equivalent area of
permanently open vent’s
14,500mm2 16,500mm2 18,500mm2 20,500mm2
Example: an appliance with a flue draught stabiliser and a rated output of 7kW would require an equivalent
area of [5 x 300] + [2 x 850] = 3200mm2
It is unlikely that a dwelling constructed prior to 2008 will have an air permeability of less than 5.0m2unless
the dwelling has received extensive measures to improve the air permeability.
Page 19 of 34
Combustion Air Ventilation Requirements for
Gas Appliances
Does the room contain a DFE fire in
an open flue?
Yes
Where a design plate or Appliance
Manual is Not available:
seek Technical Advice
Does the room contain a
fuel burning appliance?
Is it a balanced
flue or room sealed
appliance?
Is it a gas
appliance of less
than 7kW
Is it a flueless gas
appliance?
Yes
Yes
Yes
Is it a Gas Appliance
from
7kW up to 37kW
No
Is it a Gas Appliance
from
37kW up to 53kW?
No
Yes
For appliances above these kW
ratings contact a registered Gas
Safe Engineer for Technical
Advice
Yes
Free Air area =
10,000mm2
Yes
Free air area
= 15,600mm2
Free air area
= 23,400mm2
No
Page 20 of 34
AIR BRICKS & VENTILATORS
There are many types of air bricks
Combustion Air Ventilation for Oil Fired Appliances
Does the room contain a fuel
burning appliance?
Yes
Is it an oil fired appliance of
5kW or under?
No
Yes
Is it an Oil Fired appliance
from 5kW up to 30kW?
Yes
No
For oil fired appliances above these kW
ratings, seek technical advice from an
approved OFTEC engineer
No
Free air area =
55mm2 x kW
rating
Page 21 of 34
VENTILATION REQUIREMENTS
FOR OPEN FLUED- GAS
APPLIANCES.
7kW and under heat input (net) does not
require additional ventilation.
The combustion air requirements for an open
flued gas appliance can be determined
using
the following:
A gas range rated appliance with a heat
input from 20kW to 25 kW (net) the
maximum heat input must be used to
determine the ventilation required.
25kW – 7kW = 18 kW
18 x 500mm
2
= 9,000mm
2
of
ventilation
required.
Note: There are different ventilation
requirements for a single gas appliance or
groups of appliances with a total input
rating over 70kW (net). Advice
regarding
these appliances should be sought
from a
registered gas safe or solid fuel
engineer
Gas Appliances in compartments
Open flued gas appliances located in
compartments which are ventilated directly
to outside require ventilators fitted at high and
low level.
The ventilators should be sized as follows:
High Level Ventilator - 500mm
2
/ kW heat input
Low level ventilator – 1000mm
2
/ total kW heat
Input Example: 20kw boiler + High Level 500 x 20
= 10,000mm
2
Low Level 1000x20 = 20,000mm
2
Heat input greater than 7kW (net) requires an
additional 500mm2 of ventilation per kW
e.g. an appliance with
15kW input requires:
15kW - 7kW = 8kW
8 x 500mm
2
= 4,000mm
2
of
ventilation
required.
Heat
input
kW
net
Room vent
free area
(mm
2
)
Heat
input
kW
net
Room vent
free
area (mm
2
)
1
0
3
14,500
2
0
3
15,000
3
0
3
15,500
4
0
3
16,000
5
0
4
16,500
6
0
4
17,000
7
0
4
17,500
8
500
4
18,000
9
1,000
4
18,500
1
1,500
4
19,000
11
2,000
4
19,500
1
2,500
4
20,000
1
3,000
4
20,500
1
3,500
4
21,000
1
4,000
5
21,500
1
4,500
5
22,000
1
5,000
5
22,500
1
5,500
5
23,000
1
6,000
5
23,500
2
6,500
5
24,000
2
7,000
5
24,500
2
7,500
5
25,000
2
8,000
5
25,500
2
8,500
5
26,000
2
9,000
6
26,500
2
9,500
6
27,000
2
10,000
6
27,500
2
10,500
6
28,000
2
11,000
6
28,500
3
11,500
6
29,000
3
12,000
6
29,500
3
12,500
6
30,000
3
13,000
6
30,500
3
13,500
6
31,000
3
14,000
7
31,500
Page 22 of 34
FLUES
To work properly and safely, fuel burning
appliances need a continuous
supply of air.
(See Technical Data Plate or Appliance
Specification for Combustion air ventilation
requirements )
Gas Fire of 7kW and under – combustion air
ventilation not normally required.
Room Sealed Balanced Flue or Oil Fired –
No Combustion Air Ventilator Required.
Oil Cooker & Boiler (lined flue) combustion air
ventilation required.
Solid fuel boiler (lined flue) combustion air
vent required
Free standing boiler combustion air vent
required
Example of a free standing stove flue
arrangement
Gas fired back boiler combustion air vent
required
Page 23 of 34
Free standing oil – fired boiler combustion air
ventilation required.
Inset Flueless gas fire (SEEK TECHNICAL
ADVICE
FLUELESS GAS FIRES
Where these appliances are only for room
heating,
and with the exception of the fuel
effect type, they have generally been exempt
from the requirement to have a permanent
vent
to provide combustion air
‘In all cases you must seek technical advice
to confirm ventilation requirements on
these appliance types.
In place of a flue, these fires use burner
technology or have a
catalytic element that
ensures that only minimal non harmful
levels of carbon are produced. In addition,
they have built-in oxygen depletion sensor
that will
shut down the fire if oxygen levels
become depleted
Considerations
Several important facts must be borne in
mind by all CWI personnel involved in the
installation process, and [particularly by the
CWI technicians
All flueless fires require a minimum
permanent combustion air vent of
10,000mm2. Further additional ventilation
will be required for appliances with a rated
input above 2.7kw net within a room, or
5.4kw net within another internal space (i.e.
hallway). The vent must lead directly outside
and must not be compromised by the CWI see
manufacturers data for specific ventilation
requirements
Flueless fires can be positioned on internal
walls, and an external survey of the building
cannot provide safe information on the fuel
burning appliances that may be inside. This
emphasizes the importance of a careful
internal survey to note the appliance type
and location. Where flueless appliances are
located on external walls, then safety checks
must be carried on each appliance before and
following the planned installation.
Where flueless appliances are located on
external walls, then safety checks must be
carried on each appliance before and
following the installation of cavity wall
insulation.
When installed in an occupied room the
minimum room volume is 1 m
3
for every 0.045
kW net or when in other internal spaces such
as hallways 0.09 kW net. For example, a 1.8
kW appliance installed in a lounge area must
have a MINIMUM room volume of 40 m
3
where the room volume is smaller it must not
be installed. It should be noted that most
main rooms in terraced houses, and many in
semi-detached properties, do
not meet this
minimum volume.
10
Page 24 of 34
GENERAL:
Flueless fire or stove (Secondary Heating
Only)
•
Highly efficient energy using appliance.
•
No flue or chimney or outside wall
required.
•
Supplementary ventilation is required.
(e.g. a small air vent, as per manufacturer's
specification - instructions) through
outside wall directly into the room
•
Supplementary to primary heating.
•
Room size restrictions apply.
CHIMNEYS.
If flues become blocked, then gasses cannot
escape to the outside.
Therefore, it is extremely important to locate
and identify flues and chimneys.
Where the brick chimney is built externally, it
is therefore easily identified, drill holes may be
positioned close to the side of the chimney,
but not in the projecting part of the chimney.
(See System Designer CWI System
Specifications for maximum / minimum
distance from edge of the flue to the injection
points)
It is worth noting that brick- built chimneys
serving open fires and boilers in houses built
before 1964 are unlikely to contain a clay flue
liner.
Flues and chimneys built into a cavity wall may
be isolated from the cavity and therefore must
be protected from possible Ingress of debris /
material into the flue.
EXAMPLES OF CHIMNEY
CONSTRUCTIONS
EXAMPLES OF CHIMNEY ROUTES
Page 25 of 34
During the pre-installation check, the line of
the flue must be identified by noting the
position of the appliance and its terminal as
shown below, the route often includes offsets
that are not obvious, either internally or
externally.
You must know which type you are dealing
with to ensure:
•
that no drilling takes place on the line of
the flue.
•
Drilling a hole into a flue
could dislodge a
piece of masonry or flue
liner that may
impede the flue gases
•
In some properties, flues may be formed
from hollow blocks or interlocking liner
pots
built into the cavity.
•
Pre-cast flues serving gas appliances are
particularly difficult to trace since both
the
internal and external walls show a
flush face. the pre-cast blocks can be in
contact
with or very close to the external
leaf, it is very easy to drill
into the flue,
even if a depth stop is fitted to
the drill.
•
Pre-cast flues can also incorporate
offsets that traverse the wall. The pre-
installation
inspection of the loft space
will help to show the line
of the flue
above first floor ceiling level.
Internal – External Chimney Routes,
Pre Cast (True Flue)
Page 26 of 34
CHECKING FLUES
AND APPLIANCES
Testing appliances
With the exception of decorative fuel effect
gas fires, flames in gas appliances must be
clear and well defined, not yellow or orange
in appearance. The appearance of the flame
will vary depending on the fuel used.
You
should check the operation of all
appliances before CWI installation.
With other types of fuel types, the
appearance of the flame may vary
depending on the fuel used.
Appliances must be operated at maximum
output for at least 5 minutes with all doors
and windows shut to ensure stable
operation under worst case conditions. A
smoke/spillage test must be
carried out in
accordance with the
appliance
manufacturer’s instructions.
General
Every flue system on an external wall must
be checked before and after installation.
It is essential that these flues remain clear
and that the combustion products are
completely discharged to the outside air.
Appropriate methods of inspection and
testing for various types of flue system are
described below.
Because of the variety of fuel-burning
appliance designs, it is sometimes difficult to
establish whether the flue performance is
satisfactory. If it is not possible to confirm
this
performance, the fuel appliance,
maintenance contractor must
carry out the
appropriate tests.
PRE-INSTALLATION CHECKS
Each appliance should be ignited and
operated prior to
CWI installation to observe
that the flue is
functioning correctly. This
allows you to
compare the performance of
the appliance during, and on completion of
the works.
Flame appearance is of particular
importance with glass-fronted gas fires.
With radiant and convector-type gas fires,
check that there are no scorch or soot
marks on the
outer casing just above the
flame enclosure,
which would indicate flue
problems.
Where a flue is found faulty, CWI
installation
should be delayed until the
appropriate
remedial action has been taken.
POST - INSTALLATION CHECKS.
Solid Fuel Appliances
Where practicable, check with the aid of a
mirror to see that no insulation material has
entered the flue. If a satisfactory visual
inspection cannot be made, a check on the
efficiency of the flue system must be carried
out using a smoke pellet to test each
appliance.
All of the smoke should be drawn into the
flue. Where there is a shared flue system, no
smoke should escape from any other opening
within the building.
In certain conditions, there may be a spillage
of smoke due to the flue being colder than
the outside air. In such cases heat the flue
and repeat the test 10 minutes later.
Where doubt remains, a fully qualified
engineer should be contacted to confirm
the integrity of the flue.
Page 27 of 34
Smoke can be generated from a smoke pellet,
but this does not generate heat. If possible
and with great care, generate heat within the
appliance (e.g. heat from a blow lamp) which
can be passed into the flue openings for one
minute just prior to repeating the smoke test.
GLASS FRONTED FIRES/BOILERS AND FLOOR
MUNTEDFREE – STANDING BOILERS.
Where an appliance is operational / working,
a spillage test should be carried out in
accordance with the manufacturer’s
instructions and visually assess that the
appliance / flue is no different in its
appearance and operation to the checks
carried out during the pre-installation process
Page 28 of 34
Gas- Fired Appliances
Under the Gas Safety (Installation and Use)
Regulations, only registered and
approved
Gas Safe registered e
ngineers are
permitted to carry out work,
such as
removing any integral part of a
boiler or gas
fire. “Work” is defined as:
a) Installing or reconnecting the fitting.
b) Maintaining, servicing, permanently
adjusting, disconnecting, repairing
altering or renewing the fitting, or
purging it of air or gas.
c) Where the fitting is not readily
moveable, changing its position and
d) Removing the fitting (but the
expression
does not include the
connection or
disconnection of a bayonet
fitting or
self-sealing connection.
e) The following procedures must be
adhered to
Carry out standard visual checks.
When carrying out a flue spillage test,
•
All doors and windows in the room
should be
closed. However, if there is an
extractor fan in any room within the
premises, includes extractor fans, fans in
open flue appliances, fans in
cooker
hoods, the circulating fans of warm air
heating systems and circulatory ceiling
fans.
•
The
test must take place with the fan in
operation and the inter-connecting doors
open.
•
Run the appliance for 5 minutes. Carry
out
a spillage test at the base of the
canopy,
draught diverter - or to the
manufacturer’s instructions. No spillage
should occur.
A suitable, smoke match holder must be
used during the spillage test process
Page 29 of 34
PASS
X FAIL
•
Using a suitable sized tube or tooling, hold
a smoke match with its tip
approximately 3
mm inside the lower edge of the canopy
of the fire. Smoke escaping outwards from
the draught diverter or
canopy indicates
spillage.
If spillage does
occur,
•
Continue to run the appliance for
10 minutes and repeat the test.
•
If spillage still occurs, switch the
appliance off. Issue warning notices and
call in the relevant fuel supplier or
in the
case of a gas appliance the gas
emergency service.
ROOM - SEALED APPLIANCE
(balanced flues)
•
Wherever possible, look inside flues and
air
inlets from an external position to
check for
obstructions.
•
Assess the appearance of the
combustion
chamber flame, compared
with how it
looked in your pre-
installation check.
•
A
well-defined flame generally means
that the
flue and airway are
unobstructed
OIL – FIRED APPLIANCES
•
Wherever possible, look inside flues and
air
inlets from an external position to
check for
obstructions. Assess the
appearance of the combustion
chamber
flame, compared with how it
looked in
your pre-installation check. A
well-
defined flame generally means that the
flue and airway are unobstructed
Page 30 of 34
Installing Firm’s Name, Address and Contact Details
(or Letterhead)
In our opinion, this appliance should not be used until such time that a fully
qualified / registered person or company has checked the appliance, open fire,
flue, boiler, and that the appropriate certification has been provided following
investigation and resulting remedial / corrective works to ensure that it is safe
to use.
Please refer to the ‘Warning Notice’ issued to you
Contact points:
Gas:
Oil
Solid Fuel
Page 31 of 34
Installing Firm’s Name, Address and Contact Details
(Or Letterhead)
In accordance with current Gas Safety (Installation and Use) Regulations
IMPORTANT – This notice concerns your safety
Issued by; (print) Company:
Technician’s signature: Date and time of issue:
Occupiers name:
Address:
Post code: Telephone number
The make of the appliance: Model Appliance type
Location of the appliance:
It is unsafe to use, because:
In the interest of safety and to comply with current Gas Safety (installation and use)
Regulations, the following action has been taken:
The appliance has been turned off and labelled
The occupier has been informed, and the appliance left connected:
The appliance has been turned off and the emergency service notified: ref no:
The occupier to sign:
I have received a copy of this Warning Notice and confirm that I understand that the use of the
installation could present a hazard and could place me in breach of the current
Gas Safety
(installation and use) Regulations,
Signed: Print Name Date
Page 32 of 34
GENERAL:
RISK ASSESSMENT RELATING TO FLUES,
CHIMNEYS AND COMBUSTION AIR
VENTILATORS:
Activity The installation of Cavity Wall
Insulation (CWI) within the external walls of
existing buildings.
Potential Hazard
•
The ingress of insulation material into
existing combustion air ventilators, flues
or chimneys during the CWI installation,
can result in the impairment of
Combustion air flow and / or the escape
of combustion air gases produced by an
existing fuel – burning appliance into the
dwelling.
RISK:
•
The risk arising from the hazard is that
carbon monoxide produced by fuel –
burning appliances will be unable escape
to outside atmosphere.
Carbon monoxide is an extremely toxic
gas and its presence is difficult to detect.
Anyone exposed to carbon monoxide is
likely to suffer fatal or very serious illness.
THOSE AT RISK:
The occupants within a building.
ELIMINATION OF HAZARD (Control of Risk)
Cavity wall insulation installers must carry out
their duties in accordance with:
•
Current regulations governing the
identified fuel types.
•
Technicians guide to best practice: ‘Flues,
chimneys and combustion air ventilators’
published by the Cavity Insulation
Guarantee Agency (CIGA)
This guide sets out the appropriate checks,
procedures and actions that must be carried
out during survey, pre – installation and
post installation of cavity wall insulation to
buildings containing fuel – burning
appliances.
THE RISK ASSESSMENT MUST INCLUDE:
ASSESS / SURVEY, IDENTIFY and RECORD
•
Primary Air Type.
•
Appliance Type.
•
Chimney / Flue Location.
•
Combustion Air Supply.
•
Secondary Fuel Type.
•
Appliance Type.
•
Combustion Air Supply Location.
Page 33 of 34
TECNICIANS SAFTY CHECKS
PRE-INSTALLATION CHECKS
•
Identify appliance, flue/chimney routes,
internal & externally.
•
Carry out a spillage test to unlit open flues
GAS.
•
Run appliance
•
View and note flame colour.
•
Check for staining to fires appliances and
surrounding decoration.
•
Check combustion gases externally
•
Appliance check (Smoke test / Spillage
test)
•
Identify combustion air supply
o Fitted
o Correct size
o Location
INSTALLATION - VISUALLY CHECK.
•
Chimney/flue routes to avoid drilling into
them
•
Chimney/flue routes for ingress of
material
•
Combustion air ventilator is
unobstructed.
POST INSTALLATION CHECKS
•
Visually check appliances for insulation
ingress into the appliance and or
chimney flues
•
Carry out a spillage test.
GAS.
•
Run appliances at maximum for at least 5
minutes
•
Visually check that flame compares with
pre-installation checks
•
Appliance check (Smoke test/Spillage
test)
•
If results are unclear, retest after a
further 10 minutes.
IF THERE IS ANY DOUBT:
1. Switch off the appliance’s (Gas) or Ensure
where practical that the solid fuel
appliance must not be used
2. Issue Warning Notice
3. Advise occupants and / or owner.
4. Call in the relevant fuel supplier or
registered maintenance contractor /
engineer
TRAINING.
All CWI installers must receive appropriate
combustible fuels awareness training to
enable them to discharge their
responsibilities relating to the prevention of
insulation ingress into appliances, flues,
chimneys and combustion air
ventilators,
and to undertake the simple safety checks
referred to within the CIGA
guide.
NOTE:
All installing companies must ensure
that their technicians have
successfully attended a
(STGW -:
Standard Training in Gas Work, HETAS /
OFTEC Awareness course)
to enable
them to
discharge their responsibilities.
This course should include solid fuel
flues and chimney awareness
The STGW course must be re-taken by
each approved technician every 5 years
being the maximum term of Certificate
.
Page 34 of 34
Technician’s safety check sheet – flues, chimneys and combustion air ventilators.
This sheet specifies the minimum checks, and actions that must be carried out during the installation of CWI to
buildings containing fuel – burning appliances.
It must be read in association with “ Technician’s guide to best practice – Flues, chimneys and combustion air
ventilators”
Survey – identify and record
• Fuel type(s)
• Appliance type(s)
• Flue, chimney location(s)
• Location of combustion air
Ventilator(s)
Pre – Installation
• Appliance identified, flue / chimney routes internally,
externally.
• Appliance run
• View and note - appearance and flame colour.
• Combustion gases checked externally.
• Appliance checked for staining and general visual
condition (smoke / spillage test)
• Smoke / spillage tests satisfactory.
• Combustion air supply compliant.
• Signs of spillage / distress to open flues, chimneys.
Installation – Visually check
• Flue / chimney routes to avoid drilling into them.
• Flue / chimney routes to avoid ingress of material
• Combustion air ventilator(s) unobstructed.
Post - Installation
• Visible signs of spillage of the cavity wall insulation
within the fire, appliance, flue.
• Appliance run at maximum for a minimum of
five minutes
• Visual check that the flame compares wit
h
pre – installation inspections.
• Smoke / spillage test satisfactory.
• If results were unclear, re- test a
fter a further
ten minutes.
• Re – test satisfactory.
If there is any doubt or questions answered “N“ then :–
1. SWITCH OFF THE APPLIANCE – OR ENSURE THAT THE SOLID FUEL APLIANCE CANNOT BE USED
2. ISSUE A WARNING NOTICE.
3. ADVISE OCCUPANTS AND OWNER.
4. CALL OUT a competent body or person such as a registered qualified supplier or maintenance contractor
(e.g. Gas Safe, Hetas, Solid Fuel, Oftec)
Installation address:
Name of Technician:
Signature:
Date: / / 202
Important -: It is the installer company’s responsibility, to ensure that the Technician is competent to discharge
these responsibilities.
Failure to carry out visual inspections or safety checks could lead to the death of an occupant and prosecution.
