Smoke from a fire can be seen in 4 different forms. Each form is called "visible smoke" and interests firefighters. Compounds in the smoke are composed of three main species, nitrogen, carbon compounds (including hydrogen compounds), and water vapor. The lighter the color of visible smoke, the more dilute it is as compared to the volume of air above it.
The 3 Types Of Fire Smoke And Residues
- Volatile Fire Smoke
This smoke is composed of incompletely burned gasses, water vapor, and a contributing amount of particulate matter. It is blue and less dense than the smoke from the entirely burned fire. This smoke product can escape from the burned burning zone of fire by greasing the outside surfaces of windows and doors or through chimney flues, ventilation ducts, and cracks in buildings intended for human occupancy. Fire smoke can get into the lungs of people when they sleep or work close to a fire. The gasses are breathed deeply into the lungs. The toxic nitrogen compounds cause irritation and long-term damage to lung tissue.
- Invisible Fire Smoke
This type of smoke does not have a smoke color and does not contribute to the visibility of fire ground operations. In other words, it is invisible to the naked eye. This type of smoke has a density similar to air and can be smelled by firefighters at some distance. This type is composed mainly of carbon compounds (including hydrogen compounds) along with some nitrogen compounds and water vapor. The visible portion consists mainly of gas molecules (containing mostly hydrogen). The smoke from an entirely burned fire will have a visible color, but it will still be invisible to the naked eye if there is insufficient heat and oxygen to support combustion. Fire smoke contains much less oxygen than air due to the pressure inside the fire caused by combustion.3. Thermal SmokeThis type of smoke occurs in smoldering fires and fires burning at low temperatures. It can be seen with a naked eye as it has visible flames and smoke but does not make much heat or sound. Firefighters often use this type of smoke to locate hot spots on fire quickly. Thermal (smoke) products are colorless and denser than air resulting in little buoyancy in their movement into surrounding areas.
- Visible Fire Smoke
This type of smoke comprises carbon compounds (including hydrogen compounds), nitrogen compounds, and water vapor. The visible portion consists mainly of gas molecules (containing mostly hydrogen). The smoke is blue and less dense than the smoke from the entirely burned fire. This fire smoke has a density similar to air and can be smelled by firefighters at some distance. It is the most common type of fire smoke used in fire fighting operations due to its intense smell, which makes it visible for a long time after a fire event. This type can escape from the burned burning zone of fire by greasing the outside surfaces of windows and doors or through chimney flues, ventilation ducts, and cracks in buildings intended for human occupancy. Fire smoke can get into the lungs of people when they sleep or work close to a fire. The gas is breathed in deeply into the lungs. The toxic nitrogen compounds cause irritation and long-term damage to lung tissue. These nitrogen compounds are carcinogenic and cancer-causing.