In general, vapor itself is not explosive. However, the vapor of certain substances can be highly flammable or explosive when combined with an ignition source such as heat, sparks, or flames.
For a substance to be flammable or explosive, it must have certain properties such as a low flash point (the minimum temperature at which it can ignite) and a lower explosive limit (LEL) or lower flammable limit (LFL) which denotes the minimum concentration of vapor in air that can ignite. When these conditions are met and an ignition source is present, the vapor can ignite and potentially cause an explosion.
Examples of flammable or explosive vapors include gasoline, propane, butane, natural gas, and various volatile chemicals. These substances have low flash points and can form ignitable mixtures with air when in vapor form.
It's important to note that the specific properties and behaviors of vapors can vary depending on the substance. It is crucial to handle and store flammable materials properly, following appropriate safety guidelines and regulations to minimize the risk of explosions or other hazards.