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Last edited 06 Aug 2021
|Workers apply intumescent paint to a floor beam at the 44th Street facility. Source: MTA Construction & Development Mega Projects.|
A fire retardant is a substance such as a coating, powder, foam, gel or spray, that is used to slow - and eventually stop - the spread of fire. It is a preventive measure that can help limit a fire’s spread by triggering a chemical reaction.
More complex fire retardants were introduced in the 19th century in the form of flame retardants for fabrics. These were developed by Joseph Louis Gay-Lussac, a French chemist who made a number of discoveries in the idea of temperature and its relationship to gas pressure (Gay-Lussac’s Law or Amontons's law).
 Fire retardant or flame retardant?
- Flame retardants are chemicals (such as aluminium hydroxide) usually applied to combustible materials (such as textiles, plastics and coatings).
- Fire retardants are chemicals (for example, ammonium and diammonium sulfate) that can also be used on surfaces, but different types of chemicals are used for different purposes. Fire retardants as extinguishers include chemicals that will absorb a great deal of heat to cool whatever has been treated. Other agents will react with the heat to put out the fire by releasing water vapour or carbon dioxide. This is a physical process called dilution. Other fire retardants are intumescent coatings (such as paints or plastic additives). These rely on substances that will expand through a chemical reaction when heated to protect the materials that have been coated. For more information see: Intumescent coatings.
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