Not Protectively Marked
Tactical Operational Guidance
Gas Mains
Part One
Aide Memoire
of incident guidance
Part Two
Flowchart
of incident guidance
Part Three
To be used in conjunction with Hazardous Materials Tactical
Operational Guidance
Document References
Relevant references
Technical references
Document Overview
Guidance for incidents involving a gas leak or fire, including domestic and
commercial installations, involving the local distribution network or fixed
installations less than 300mm in diameter excluding cylinders.
For incidents involving a gas main greater than 300mm in diameter also refer to
H3.3.0 Pipelines Tactical Operational Guidance.
Page 1 of 7
NOT PROTECTIVELY MARKED
Gas Mains
Part One – Aide Memoire
1
Initial considerations
En route
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Approach upwind/uphill if possible.
Initial crew briefing
Consider available in-cab information
External prompts: vapour clouds, pools,
fires, noise and smells
 Cautious approach
 Start risk assessment process
 Turn on gas monitoring equipment if
available
 Eliminate potential ignition sources:
 Turn off mobile phones
 Use intrinsically safe equipment
On arrival
 Gather initial information:
o Any fire?
o Leak or rupture?
o Gas rising or low level?
o Liquid: pooling, flowing, vapourising?
 Identify and address any immediate risks
 Do not extinguish fire at leak
2
Detailed information gathering
 Establish extent and overview:
o Size of main/leak
o Slope of ground
o Wind direction
o Built environment
 Consider multiple sources of information
(360° survey/MDT/ owner/occupier/
witnesses/SSRI)
3
 Share and gain situational awareness
with other responders
 FireMet/CHEMET
 Ensure all relevant risk information is
communicated: consider METHANE
message
Resource information
 Consider PDA/ETA
 Initiate a make up if necessary for:
o Public evacuation
o Gas monitoring
 Consider other agencies – gas supplier, EA,
local authority, Public Health England
4
 Initial cordon upon advice, SSRI or MDT
60m for suburban area
 Balance risk against benefit
 Evacuate people at risk
 Eliminate ignition sources
 Protect surrounding risks
 Inform others
 Consider police for evacuation
 Identify how resources will be managed:
o Establish and maintain safe access
and egress
o RVP/marshalling areas
o Deployment site plan
Risk information to inform planning
Key hazards
Key control measures
 Flammable atmosphere leading to explosion
(LPG/natural gas)
 Ignition of flammable atmosphere
 Excessive noise (escaping gas)
 Irrespirable atmosphere
 Fire heat and smoke
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Page 2 of 7
Isolation of services
Approach upwind
Minimum personnel in risk area
Establish and maintain cordons
Ear protection
Fire hoods up
NOT PROTECTIVELY MARKED
Gas Mains
 Flying debris/dust
 Projectiles due to explosion
 Structural collapse
5
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Intrinsically safe equipment
Tactical ventilation
Safety jet
Covering jet
BA procedures
Attendance of utilities rep
Gas monitoring
Dispersal/containment jet
Advice from HMEPA
On site specialist advice
Adherence to on site warning signs
Appropriate PPE as indicated by
EAC/APP code
Eye protection
RPE
Avoidance routes
USAR/Technical rescue team
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Correctly resourced
Communicated and understood
Flexible
Resilient e.g. ‘plan B’
Regularly reviewed
Be prepared to brief/hand over
Planning
Common prompts
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Clear plan, prioritised objectives
Based on relevant information
Follows a logical sequence
Appropriately delegated
Balances risks and benefits
Aligns to Tactical Mode
Incident specific prompts
Leaks/ruptures
 Reposition appliances taking into account
size and scale of leak (see supporting
information)
 Consider additional PPE/RPE
 Evacuate area
 Identify & remove ignition sources e.g.
divert traffic, prohibit smoking, no mobile
phones, pagers
 Liaise with HMEPA
 Request gas supplier
 Request CHEMET information
 Liaise with police
 Establish maintain and review cordons (see
supporting information)
 Establish rendezvous points
 Be aware of gas pockets/clouds
Page 3 of 7
Fires
 Reposition appliances taking into
account size and scale of fire
 Consider additional PPE/RPE
 Evacuate area
 Liaise with HMEPA
 Request gas supplier
 Liaise with police
 Establish maintain and review cordons
 Establish rendezvous points
 Protect the surrounding area from
radiated heat and direct flame
impingement using covering sprays;
o Prevent water from extinguishing
flame and entering gas main
 Extinguish by isolating the supply
 Extinguishing by any other means must
be based on a risk benefit analysis
NOT PROTECTIVELY MARKED
Gas Mains
 Water sprays:
o To isolate gas from ignition sources
o To disperse gas clouds (in still
conditions)
 Ventilate affected areas
 Handover to gas supplier
6
 Assess pipe work for damage from
direct flame contact or radiant heat
 Handover to gas supplier
Command and control
 As per generic guidance.
7
Safety and welfare
 Shelter/support for displaced residents
8
Communications
 Use of intrinsically safe equipment at a gas leak
9
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10
Liaison
Gas supplier/utility companies
Police
Local authority
FRS media department
Closing stages and post incident consideration
 Scaling down operations and removing cordons to reduce impact on the community
 Scene preservation, logging of FRS photo evidence and investigation
Supporting/additional information
Type of event
Pipeline
diameter
Maximum thermal hazard range
(in metres)
0-19 bar
19-40 bar
1-25mm equivalent
leak diameter
All
5
5
25-75mm equivalent
leak diameter
All
11
18
75-150mm equivalent
leak diameter
All
25
33
168mm (6”)
25
55
324mm (12”)
50
70
Rupture
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“Leaks” are anything below a 150mm diameter (or equivalent) opening
“Ruptures” are anything greater than a 150mm
Regional transmission pipelines range from 7 to 40 bar
Distribution mains operate up to 7 bar
Page 4 of 7
NOT PROTECTIVELY MARKED
Gas Mains
Flammable atmosphere
If a gas/air mixture comes within its flammable range and an ignition source is present, a
fire or explosion could result in serious injury such as flash burns and building damage.
Gas escapes
In buildings - Gas can travel and accumulate in a building as a result of leakage from
one of a number of sources e.g. from broken pipes, leaking joints, corroded services,
damaged gas riser pipes on the external walls of properties; or they can arise from the
direct interference by others.
In the open - Pipelines fail because of: breaks usually caused by mechanical damage,
leaks from joints and flanges and malicious damage. The preferred route of the gas is
upwards. Underground fissures, ducts, voids and cellars can provide a conduit for it to
travel considerable distances from the point of origin i.e. sewers, service tunnels.
Odourisation
Natural gas, being 94.6% methane, has little or no smell. The odourant, tertiary butyl
mercaptan (TBM) is used to impart the distinctive sulphur smell and is only present at
pressures under 7 bar.
Asphyxiation
Natural gas is lighter than air and colourless and will displace the air in the space it is
entering, thus creating an increasingly irrespirable atmosphere leading to asphyxiation.
Noise induced hearing loss
Gas escaping from a medium or high pressure pipeline can be extremely loud with the
potential for damage to hearing.
Page 5 of 7
NOT PROTECTIVELY MARKED
Gas Mains
Part Two - Flowchart
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Incident info
Establish extent and
overview:
o Size of main/leak
o Slope of ground
o Wind direction
o Built environment
Consider multiple
sources of information
(360o survey/MDT/
owner /occupier/
witnesses/ SSRI)
External prompts:
Vapour clouds, pools,
fires, noise and smell
Share and gain
situational awareness
with other responders
Ensure all relevant risk
information is
communicated;
consider METHANE
message
Consider
In-cab information
Resource management
Consider media impact
FireMet/CHEMET
Reposition appliances
taking into account size
and scale of leak (see
supporting information)
Closing stages
 Scaling down operations
and removing cordons to
reduce impact on the
community
 Scene preservation,
logging of FRS photo
evidence and
investigation
Page 6 of 7
En route brief
On arrival










Initial crew briefing
Cautious approach
Approach upwind/uphill
Start risk assessment
Gather information:
o Any fire, leak or
rupture?
o Gas rising or low level?
o Liquid: pooling, flowing,
vaporising?
Identify and address any
immediate risks
Balance risk v benefit
Turn on gas monitoring
equipment if available
Eliminate potential ignition
sources:
o Turn off mobile phones
o Use intrinsically safe
equipment
Inform others
Safety critical actions
 Do not extinguish fire at
leak
 Initial cordon upon advice,
SSRI/MDT 60m
 Isolate services
 Protect surrounding risks
 Intrinsically safe equipment
 Consider additional PPE/
RPE
 Evacuate area
 Identify and remove
ignition sources e.g. divert
traffic, prohibit smoking,
no mobile phones, pagers
 Liaise with HMEPA
 Establish maintain and
review cordons (see
supporting information)
 Be aware of gas pockets/
clouds
 Water sprays - to isolate
gas from ignition sources,
to disperse gas clouds,
ventilate affected areas
NOT PROTECTIVELY MARKED
Resources info
 PDA/ETA
 Make up if
necessary: public
evacuation, gas
monitoring
 Return resources not
required
 Other agencies: gas
supplier, EA, local
authority, Public
Health England
 Safe access/egress.
 RVP/marshalling
 Deployment site plan
 Police for evacuation
Key hazards
 Flammable
atmosphere leading
to explosion
(LPG/natural gas)
 Ignition of Flammable
atmosphere
 Excessive noise
(escaping gas)
 Irrespirable
atmosphere
 Fire, heat and smoke
 Flying debris and
dust
 Projectiles due to
explosion
 Structural collapse




As incident develops
Flexible
Resilient e.g. ‘plan B’
Regularly reviewed
Be prepared to
brief/hand over
Gas Mains
Part Three – Document References
1.
Relevant references
This incident type is potentially linked to the following other operational guidance
documents:
Document name
Link to document
To be populated
2.
Technical references

None
Ref no:
Date of issue:
Version no:
Page 7 of 7
H2.0.0
13/10/2014
1
Lead FRS:
Bedfordshire
Review date:
12/10/2014
Protective
marking:
NOT PROTECTIVELY MARKED
None