Environmental protection agencies banned halon in the 1990's, creating a need for alternatives. Alternatives to halon must extinguish most types of fires, while remaining safe for people and equipment. Since halon was banned, several fire suppression agents and technologies have emerged. In this post, we will explore one of these halon replacements: aerosol fire suppression systems.
How Aerosol Suppression Agents Work
Aerosol fire suppression uses a combination of microparticles and gaseous matter to flood the protected area. The particles are in a vapor state until discharged from the device. On release, a chain reaction produces solid particles and gaseous matter to suppress the fire.
To suppress a fire, the suppression agent must break the fire tetrahedron. That means that suppression chemicals must reduce the fuel, remove oxygen, remove heat, or hinder a chain reaction. As long as there is enough heat, fuel, and oxygen present, a fire will keep burning. Aerosol fire suppression systems work by removing heat:
- Aerosol systems release large microparticles that surround the flame
- On contact, the particles cool the flame and absorb heat to suppress the fire
Aerosol fire suppression systems can also work by disrupting a chain reaction:
- Aerosol particles containing potassium nitrate can act as oxidizers
- These particles bind with the free radicals that sustain the fire’s combustion to produce by-product molecules, such as potassium hydroxide and water.
- This disrupts the combustion process until the fire is out.
How Effective are Aerosol Systems?
Aerosol fire suppression systems can be effective in suppressing Class A, B, and C fires. However, effectiveness depends on the concentration of particulates near the flame, location of other flammable materials, and type of fuel involved.
Aerosol fire suppression systems can be equipped with either electrical or automatic fire detection and activation. Aerosol suppression is available for both a total flooding environment and for local applications.
Are Aerosol Fire Suppression Systems Safe?
Aerosol fire suppression systems function through a chemical reaction that also generates heat. Consequently, the temperature of the canisters can reach 4000°F at discharge. This can be a disadvantage for aerosol fire suppression systems, because the high temperature may lead to re-flash of the fire. Some aerosol fire suppression systems feature cooling blocks that lower the temperature and prevent re-flash.
Aerosol fire suppression systems do not typically damage equipment. However, large aerosol particles can leave residue on sensitive components. Try to install aerosol fire suppression systems away from any sensitive electronics. This is not always possible when installing in tight areas like the nacelle of a wind turbine.
Aerosol fire suppression systems should not be used in occupied spaces, because aerosols can be dangerous if inhaled. Similarly, aerosols create visual impairment, which can complicate evacuation. There have been two tragic incidents from false discharges of aerosol systems in a bank vault, which killed eight and injured seven, and on a fishing vessel, which led to one death.
If an aerosol system discharges in an unoccupied space like a CNC machine, wait to vent the system before assessing any damage.
Clean agents are a safer alternative to aerosols for occupied spaces. Clean agents are safe for people, and they do not leave residue on equipment.