Flammable vs Inflammable: What Is The Difference?

While they are often confused with each other or dismissed as the same, there are important distinctions between flammable vs inflammable substances that your business needs to be aware of if it uses or transports such materials. Not only will this enable you to comply with UK Control of Substances Hazardous to Health (COSHH) regulations, but it means your employees can better understand the substances they work with, respect the volatility and risks associated with them, and use care and best practices to reduce the possibility of a catastrophic accident. Here, we explain the difference between flammable vs inflammable substances


Flammable means that the substance can easily be set on fire - for example, wood and paper. Other materials to be aware of would include flammable liquids, like spirits and petrol, as well as flammable gas, such as propane. Because flammable materials are considered a serious fire risk, you must ensure that any and all relevant materials are recorded in your fire risk assessment and that every reasonable measure is taken to reduce the likelihood and impact of an accident. This includes the use of flammable hazard signs to inform employees and visitors as to the risk. 


Combustible materials are similar to flammable materials, but with a subtle difference. To understand this, it’s important to consider how flammable substances catch fire. Flammable and combustible materials all have a flash point - a temperature at which the substance releases vapours that can easily catch fire if exposed to a source of ignition. Therefore, the lower a substance's flash point, the more hazardous it is. While this varies greatly depending on the material, flammable substances usually have a flash point of below 37.8 oC, while combustible substances have a flash point between 37.8 oC and 93 oC. You should ensure any combustible substances your business uses are clearly marked with appropriate hazard signs.


While the word may imply a non-flammable substance, it is a common misconception. Where a flammable object can be set fire to, requiring a source of ignition, an inflammable substance can catch fire all by itself and includes unstable chemicals like some types of compressed gas and explosive hazards. Due to its extreme volatility, it’s vital that inflammable substances are handled and stored correctly. 

While the may appear the same, the difference between flammable and inflammable substances is crucial to understand. Remember, flammable substances can be set fire to (with a source of ignition), while inflammable can catch fire by themselves (without needing a source of ignition). 

For more resources on various types of dangerous substances, visit our hazards resources page.

Darren Taylor, managing director of UK Safety Store
With over 30 years' experience in the manufacturing and regulations of safety signs, our managing director Darren prides himself on providing the very best services and insights for all UK Safety Store customers.