The one-stop guide to working with flammable material: from hazard classification to mitigating risks
What are flammables?
Flammable materials are those gases, liquids, and solids that upon exposure with an ignition source (e.g. open flames, sparks, heat-producing chemical reactions, etc.) will ignite and continue to burn in air. Many flammable solids and liquids are volatile meaning they continually give off vapours that combine with air. It is these vapours that ignite and burn (not the liquids or solids themselves).1 A liquid or solid’s flashpoint is the lowest temperature at which enough vapour is given off to form an ignitable air-vapour mixture immediately above the surface.
In addition to the potential to cause fires, flammable materials can also exacerbate the hazards of other materials such as triggering explosive chemicals. Moreover, when flammable vapors burn, they often produce substantial amounts of heat and thick clouds of toxic smoke, which can also pose health hazards.
The ‘flame’ pictogram is used to represent 12 physical GHS hazard classes
|
Hazard Class |
Category |
Signal Word |
Hazard Statement |
|
| Flammable gases |
Category 1 A: (i) Flammable gas Gases at 20°C and 101.3 kPa that are ignitable when in a mixture of 13% or less by volume in air; or have a flammable range with air of a least 12 percentage points regardless of the lower flammability limit (unless data indicates the criteria for Category 1B is met). (e.g. hydrogen) |
Danger | Extremely flammable gas | H220 |
|
(ii) Pyrophoric gas: Spontaneously ignites in air at a temperature of 54°C or below. |
Danger | Extremely flammable gas May ignite spontaneous if exposed to air |
H220 H232 |
|
|
(iii) Chemically unstable gas: (a) A Chemically unstable at 20°C and 101.3 kPa. |
Danger |
Extremely flammable gas May react explosively even in the absence of air |
H220 H230 |
|
|
(b) B Chemically unstable at > 20°C and/or > 101.3 kPa. |
Danger |
Extremely flammable gas May react explosively even in the absence of air at elevated pressure and/or temperature |
H220 H231 |
|
|
Category 1 B Gases that meet the flammability criteria for Category 1A, but which are not pyrophoric, nor chemically unstable, and which have at least either: a lower flammability limit of more than 6% by volume in air; or a fundamental burning velocity of less than 10 cm/s. |
Danger |
Extremely flammable gas |
H221 |
|
|
Category 2 (no pictogram) Gases other than Category 1A and 1B, which have a flammable range while mixed in air at 20°C and 101.3 kPa. |
Warning |
Extremely flammable gas |
H221 |
|
| Flammable liquids |
Category 1
Flash point < 23°C and initial boiling point ≤ 35°C (e.g. diethyl ether) |
Danger |
Extremely flammable liquid and vapour |
H224 |
|
Category 2 Flash point < 23°C and initial boiling point > 35°C (e.g. acetone). |
Danger |
Highly flammable liquid and vapour |
H225 |
|
|
Category 3 Flash point ≥ 23°C and ≤ 60°C (e.g. xylene). |
Warning |
Flammable liquid and vapour
|
H226 |
|
|
Category 4 (no pictogram required) Flash point > 60°C and ≤ 93°C (e.g. benzaldehyde, nitrobenzene) |
Warning |
Combustible liquid |
H227 |
|
|
Pyrophoric liquids |
Category 1 Ignites within five minutes when added to an inert carrier and exposed to air, or it ignites or chars a filter paper on contact with air within five minutes.
|
Danger |
Catches fire spontaneously if exposed to air
|
H250 |
|
Flammable solid |
Category 1 (e.g. Mg) Metal powders with a burning time ≤ 5 min and substances or mixtures with a wetted zone that does not stop fire and a burning time < 45 s or burning rate > 2.2 mm/s. |
Danger |
Flammable solid |
H228 |
|
Category 2 (e.g. camphor) Metal powders with a burning time > 5 min and ≤ 10 min and substances or mixtures with a wetted zone that stops the fire for at least 4 min and a burning time < 45 s or burning rate > 2.2 mm/s.
|
Warning |
Flammable solid |
H228 |
|
|
Pyrophoric solid |
Category 1 Ignites within five minutes of encountering air.
|
Danger |
Catches fire spontaneously if exposed to air
|
H250 |
| Aerosols |
Category 1 Any aerosol that contains ≥ 85% flammable components (by mass) with a heat of combustion ≥ 30 kJ/g, and (if applicable) an ignition distance ≥ 75 cm (for spray aerosols) or a flame height ≥ 20 cm and a flame duration ≥ 2 s; or a flame height ≥ 4 cm and a flame duration ≥ 7 s (for foam aerosols). |
Danger |
Extremely flammable aerosol Pressurized container: may burst if heated |
H222 H229 |
|
Category 2 Any aerosol that dispenses a spray with an ignition distance < 75 cm and which has (i) a heat of combustion ≥ 20 kJ/g; or (ii) a heat of combustion < 20 kJ/g with an ignition distance ≥ 15 cm; or (iii) a heat of combustion < 20 kJ/g and an ignition distance <15 cm along with either a time equivalent ≤ 300 s/m3 or a deflagration density ≤ 300 g/m3. Any foam aerosol, which has a flame height ≥ 4 cm and a flame duration ≥ 2 s. |
Warning |
Flammable aerosol Pressurized container: may burst if heated |
H223 H229 |
|
|
Category 3 (no pictogram) Any aerosol that contains ≤ 1% flammable components (by mass) with a heat of combustion < 20 kJ/g; or any aerosol that contains > 1% (by mass) flammable components or has a heat of combustion ≥ 20 kJ/g but does not meet the criteria for Category 1 or 2. |
Warning |
Pressurized container: may burst if heated |
H229 |
|
|
Chemicals under pressure  |
Category 1 Contains ≥ 85% flammable components (by mass) and has a heat of combustion of ≥ 20 kJ/g. |
Danger |
Extremely flammable chemical under pressure: may explode if heated |
H282 |
|
|
Category 2 Contains > 1 % flammable components (by mass); and has a heat of combustion < 20 kJ/g; or contains < 85% flammable components and has a heat of combustion ≥ 20 kJ/g. |
Danger |
Flammable chemical under pressure: may explode if heated |
H283 |
|
Self-reactive substances and mixtures |
Type B Has explosive properties, and as packaged, neither detonates nor deflagrates rapidly, but is liable to undergo a thermal explosion in that package.  |
Danger | Heating may cause a fire or explosion | H241 |
|
Type C Has explosive properties, and as packaged cannot detonate or deflagrate rapidly or undergo a thermal explosion. |
Danger | Heating may cause a fire | H242 | |
|
Type D (i) Detonates partially, does not deflagrate rapidly, and shows no violent effect when heated under confinement; or (ii) does not detonate at all, deflagrates slowly, and shows no violent effect when heated under confinement; or (iii) does not detonate or deflagrate at all and shows a medium effect when heated under confinement. |
Danger | Heating may cause a fire | H242 | |
|
Type E Neither detonates nor deflagrates at all and shows low or no effect when heated under confinement.
|
Warning | Heating may cause a fire | H242 | |
|
Type F Neither detonates in the cavitated state nor deflagrates at all and shows only a low or no effect when heated under confinement in addition to low or no explosive power. |
Warning | Heating may cause a fire | ||
|
Type G (no pictogram) Neither detonates in the cavitated state nor deflagrates, showing no effect when heated under confinement nor any explosive power, provided it is thermally stable (self-accelerating decomposition temperature is 60 ͦ C to 75 ͦ C for a 50 kg package). Also, liquid mixtures that have a diluent (used for desensitization) with a boiling point ≥ 150 ͦ C. |
None | No hazard statement | None | |
|
Self-heating substances and mixtures |
Category 1 Undergoes dangerous self-heating when tested in a 25 mm sample cube at 140 ͦ C.
|
Danger |
Self-heating; may catch fire |
H251 |
|
Category 2 Undergoes dangerous self-heating when tested in (i) a 100 mm sample cube at 140 ͦ C, and the substance or mixture is to be packed in packages with a volume of more than 3 m3, or (ii) a 100 mm sample cube at 140 ͦ C in addition to a 100 mm cube sample at 120 ͦ C, and the substance or mixture is to be packed in packages with a volume of more than 450 L, or (iii) a 100 mm sample cube at 140 ͦ C in addition to a 100 mm cube sample at 100 ͦ C.
|
Warning |
Self-heating in large quantities; may catch fire |
H252 |
|
|
Substances and mixtures that emit flammable gases upon contact with water |
Category 1 Reacts vigorously with water at ambient temperatures and demonstrates a (general) tendency for the gas produced to ignite spontaneously, or which reacts readily with water at ambient temperatures such that the rate of evolution of flammable gas ≥ 10 L/kg of substance over any one minute. |
Danger |
In contact with water releases flammable gases which may ignite spontaneously |
H260 |
|
Category 2 Reacts readily with water at ambient temperatures such that the maximum rate of evolution of flammable gas ≥ 20 L/kg of substance per hour, and which does not meet the criteria for Category 1. |
Danger |
In contact with water releases flammable gases |
H261 |
|
|
Category 3 Reacts slowly with water at ambient temperatures such that the maximum rate of evolution of flammable gas is > 1 L/kg of substance per hour, and which does not meet the criteria for Categories 1 and 2. |
Warning |
In contact with water releases flammable gases |
H261 |
|
|
Organic peroxides |
Type B Has explosive properties and as packaged, neither detonates nor deflagrates rapidly, but is liable to undergo a thermal explosion in that package. |
Danger |
Heating may cause a fire or explosion |
H241 |
|
Type C Has explosive properties and as packaged cannot detonate or deflagrate rapidly or undergo a thermal explosion. |
Danger |
Heating may cause a fire |
H242 |
|
|
Type D (i) Detonates partially, does not deflagrate rapidly, and shows no violent effect when heated under confinement; or (ii) does not detonate at all, deflagrates slowly and shows no violent effect when heated under confinement; or does not detonate or deflagrate at all and shows a medium effect when heated under confinement. |
Danger |
Heating may cause a fire |
H242 |
|
|
Type E Neither detonates nor deflagrates at all and shows low or no effect when heated under confinement.
|
Warning |
Heating may cause a fire |
H242 |
|
|
Type F Neither detonates in the cavitated state nor deflagrates at all and shows only a low or no effect when heated under confinement as well as low or no explosive power.
|
Warning |
Heating may cause a fire |
H242 |
|
|
Type G (no pictogram) Neither detonates in the cavitated state nor deflagrates, showing no effect when heated under confinement nor any explosive power, provided it is thermally stable (self-accelerating decomposition temperature is 60 ͦ C or higher for a 50 kg package). Also, liquid mixtures that have a diluent (used for desensitization) with a boiling point of not less than 150 ͦ C.
|
None |
No hazard statement |
None |
|
|
Desensitized explosives |
Category 1 Corrected burning rate (AC) ≥ 300 kg/min but not more than 1200 kg/min. |
Danger |
Fire, blast projection hazard; increased risk of explosion if desensitizing agent is reduced |
H206 |
|
Category 2 Corrected burning rate (AC) ≥ 140 kg/min but < 300 kg/min. |
Danger |
Fire or projection hazard; increased risk of explosion if desensitizing agent is reduced |
H207 |
|
|
Category 3 Corrected burning rate (AC) ≥ 60 kg/min but < 140 kg/min. |
Danger |
Fire or projection hazard; increased risk of explosion if desensitizing agent is reduced |
H207 |
|
|
Category 4 Corrected burning rate (AC) < 60 kg/min.
|
Warning |
Fire hazard; increased risk of explosion if desensitizing agent is reduced
|
H208 |
How to mitigate the risks of working with flammables
1. Receiving:
- Keep a record of the flammables in your lab. When you receive flammables, make note of important information including the day it was opened, package size, and storage location. Maintaining an updated list of chemicals in your laboratory prevents an excess of chemicals and allows you to easily dispose of materials past their expiration date.
2. Storage:
- Use fire resistant storage cabinets. Your local government agency may have guidelines on the types of cabinet and shelving you may use.
- Store flammables away from incompatible chemicals. This may include combustibles, explosives, corrosives, and oxidizers.
3. Handling:
- Wear appropriate PPE when handling flammable materials including standard safety equipment like gloves, goggles, closed toed shoes as well as more specialized attire such as flame retardant lab coats.
- Work with flammables in the fume hood and ensure proper ventilation.
- Use an appropriate carrier or container when transporting flammable materials to decrease the likelihood of spills and physical damage to the bottle.
4. Awareness of surroundings:
- Remove all items that could cause flames or sparks such as electrical equipment and burners.
- Ensure proper ventilation in the laboratory and regulate the temperature or pressure if possible.
5. Emergencies and spills:
- Have a clear path between your work area and the closest emergency exit.
- Ensure emergency equipment is nearby and operational including:
- Spill kits
- First aid kits
- Fire extinguishers
6. Alternatives:
- Examine your SOP and SDS: if possible substitute reagents with low flash points and boiling points for reagents with higher flash points and boiling points.
7. Waste:
- Dispose of flammable waste in appropriate containers. Flammable cans are commonly used, but if this is not possible, put the waste back into its original container. Solid waste including rags or towels soaked in flammable liquids should also be stored in a flammable waste container.
- Store your flammable waste away from other chemicals, label it appropriately and arrange to have it removed as soon as possible to decrease the chance of spills.
