Let's talk about the general usage. Explosion-proof lights are designed to be used in a "Hazardous Location," as defined by the Canadian Electrical Code as well as other codes or regulations across different jurisdictions. Broadly speaking, a hazardous location in this context is an area where there are high enough concentrations of combustible materials in the air to cause a fire or explosion. This could be in the form of a gas (e.g. natural gas, ethanol, toluene, etc), a dust (e.g. grain, flour, coal, etc), or even a fibre. When these hazards are present, workers need to (by law) use specially designed equipment to reduce the risk of igniting the flammable materials lest they cause a catastrophic fire or explosion. For more background on the classification of hazardous locations, see our quick primer on the topic here.