Instruction Sheet
Acetylene
Recommendations for fire brigade response
when at risk through acetylene
May 2011
Liability disclaimer: This document was prepared with the greatest care by gfpa
experts and adopted by the gfpa Executive Committee. It is the responsibility of each
user to check that the latest version is on hand and applicable to each specific case.
The liability of gfpa and those involved in the preparation of the document is excluded.
Terms of contract: gfpa makes reference to the necessity to agree the specific
performances separately when signing contracts, with reference to gfpa documents.
gfpa accepts no claims to recourse of any kind, especially those arising from the
inexplicit drafting of contracts.
This document supersedes the previous “Acetylene” instruction sheet from the year
2000.
Contents:
1. Properties of Acetylene
2
2. Recognition Features
3
3. Indications
3
4. Characteristics of Acetylene Decomposition
3
5. Measures
4
6. References
6
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Released by the gfpa Executive Committee on 09 Nov. 2011 Published in English in November 2014 Technical-Scientific Advisory Board (TAB)
of the gfpa - German Fire Protection Association
Vereinigung zur Förderung des Deutschen Brandschutzes e.V.
Postfach 1231, 48338 Altenberge
Page 2 / 4 1.
Properties of Acetylene
Chemical-physical properties
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Highly flammable gas
Tends to decompose spontaneously as it is chemically unstable
Colourless, odour often like garlic or rubber (technical manufacture)
Safety parameters
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Ignition temperature: 305 °C
Explosive range: 2.3 – 83 % Vol.
Tends to decompose spontaneously in higher concentrations
Odour threshold: 240 ppm = 0.024 % Vol. (see above for odour)
Storage: Dissolved under pressure in acetone or DMF (dimethylformamide), pressure of
older cylinders approx. 8.5 bar, newer cylinders up to 19 bar
Slightly lighter than air (molar mass: 26 g/mole, density ratio: 0.9)
Explosion protection: Temperature Class T 4, Group IIC
Special hazards
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If an acetylene cylinder is exposed to a temperature of over 100 °C over a longer period,
hydraulic explosion can occur (pressure vessel rupture)!
If the cylinder bursts, a fireball with a diameter of up to 30 m can develop with additional
hazard from flying debris!
2. Recognition Features
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Odour (see Item 1)
Cylinder colour: maroon (N.B. older cylinders can still have a different colour, e.g. in
Germany: yellow, even though this has not been permitted since 1 Jan, 2007!)
Clip lock and oval hand wheel on gas cylinders
No “hollow sound” when knocked (reason: porous fill mass and acetone/DMF)
UN Number: 1001, Hazard Identification Number: 239
Hazard Placard 2.1 (red with flame and a 2 in the lower corner)
Hazard symbol “Extremely Flammable”(F+) or GHS Symbols 02 (Flame) + 04 (gas
cylinder)
3. Indications
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Explosive limit warning device (ensure proper calibration!)
Odour (see Item 1)
If using detection tubes etc., explosion protection measures must be observed!
gfpa – TAB Instruction sheet “Acetylene” May 2011 Page 3 / 4 4. Characteristics of Acetylene Decomposition
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Risk of decomposition if the temperature of the cylinder exceeds approx. 300 °C
Temperature rises without any external influences (in the event of a flashback, heating
begins near the valve)
When burning, no bright flame but rather discoloration through admixtures of soot/smoke
Abnormal odour
Irregular sound of gas flow
o N.B.: A sudden stop of the escape of gas does not necessarily mean that the
cylinder is actually empty; valve blockage possible!
5. Measures
Basic measures
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The most important measure is intensive cooling of the cylinder to prevent/stop acetylene
decomposition.
Keep unnecessary personnel away.
Safety distances:
o Personnel wearing self-contained breathing apparatus (SCBA) and proximity
suits (e.g. for cooling from behind cover):
minimum 20 m
o Personnel behind cover:
minimum 50 m
o Persons without cover:
minimum 300 m
Only use gas cylinder recovery containers or sealing devices which are authorised for
acetylene.
Do not shake cylinder if possible; do not manipulate the valve during fire brigade
response1
Fight surrounding fires quickly and effectively.
Highest risk of bursting when gas flows out with a shrill, whistling noise (= very high
pressure).
Measures when gas is leaking without any fire
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Considerable risk of explosion in closed rooms (large explosive range). Ventilate rooms,
check explosion hazard.
Observe explosion protection, eliminate ignition sources, clear hazard zone.
If pure gas without soot is escaping, close cylinder valve.
Check cylinder for heating (thermographic camera, remote thermometer, water spray jet,
back of hand where possible).
o N.B. If water dries off quickly, do not also check by hand.
o N.B.: If heating is rapid (or possibly point by point), rupture of the cylinder is
imminent!
If the cylinder is more than “hand warm”, there is a risk of decomposition. Cool the
cylinder immediately and vigorously from behind cover!
1
The fire brigade is usually too late on the scene to take effective action by immediately closing the valve. gfpa – TAB Instruction sheet “Acetylene” May 2011 Page 4 / 4 Measures when burning gas is leaking
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Evacuate the major risk area (hot zone).
Do not attempt to close cylinders which have been burning at the valve for more than 60
seconds1. Cool cylinder and allow gas to burn off.
Flashbacks from the nozzle are unlikely.
Measures for cooling heated acetylene cylinders
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Open all windows and doors (ventilation/pressure relief)
Take cooling measures from behind cover if possible (powerful spray jet). After 30
minutes, briefly interrupt cooling and check to find out if cylinder is re-heating. The faster
the cylinder warms up again, the greater the risk of explosion.
If the cylinder remains cool, immerse it in a water bath with the valve upwards. If
absolutely necessary, the cylinder can be transported in the water bath to a safe place.
To stop decomposition inside the cylinder, it must be cooled for at least 24 hours.
Do not dismantle cylinder racks; apply water ensuring that the cylinders on the inside are
also cooled.
Shooting acetylene cylinders
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Heated acetylene cylinders can be perforated with suitable ammunition fired by special
police or army units from a safe distance, thus relieving the pressure.
This measure is only possible under certain conditions (free line of fire from behind cover;
safety distance of up to several hundred metres for third parties due to risk of ricocheting)
and requires trained marksmen.
o The cylinder does not explode on impact, the gas flows off and it may be
necessary to use suitable ammunition to ignite it so that an explosive
atmosphere does not develop.
Follow-up measures
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Do not dismantle cylinder racks
Mark cylinders accordingly after a fire
Return cylinders to filling plant or have them picked up
Notify cylinder owner and supplier/manufacturer
6. References (German only)
- U. Cimolino (Hrsg.), Einsatzleiterhandbuch Feuerwehr, ecomed, Landsberg, Stand 2007
- Industriegaseverband: IGV-Kurzinformation, Stand 7/2005
- BMA: Technische Regeln für Acetylenanlagen und Calciumcarbidlager (TRAC)
- BMA: Merkblatt zur Verhütung von Acetylenflaschen-Explosionen, Anlage zur TRAC
208, BArbBl. 01/1999
- Landesumweltamt NRW: Informationssystem Gefährliche Stoffe (IGS-Fire), 09/2010
- Data sheet of the company “Linde AG”, April 2008
gfpa – TAB Instruction sheet “Acetylene” May 2011