Fire retardant
![]() |
Workers apply intumescent paint to a floor beam at the 44th Street facility. Source: MTA Construction & Development Mega Projects. |
Contents |
[edit] Introduction
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.
[edit] History
The earliest form of fire retardants (which were thought to have originated many centuries ago) were substances such as vinegar, alum and clay that were used to treat timber and some fabrics.
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).
His exploration of the use of salts as fire retardants was groundbreaking, but it wasn’t until the 1900s that more effective measures would be introduced in the form of flame retardants.
[edit] Fire retardant or flame retardant?
Modern fire retardants and flame retardants have similar purposes - to control fires - but they achieve this by different methods:
- 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.
NB Fire retardants can also be dropped from planes to extinguish forest fires.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Grenfell Tower fire – eight years on
A time to pause and reflect as Dubai tower block fire reported just before anniversary.
Airtightness Topic Guide BSRIA TG 27/2025
Explaining the basics of airtightness, what it is, why it's important, when it's required and how it's carried out.
Construction contract awards hit lowest point of 2025
Plummeting for second consecutive month, intensifying concerns for housing and infrastructure goals.
Understanding Mental Health in the Built Environment 2025
Examining the state of mental health in construction, shedding light on levels of stress, anxiety and depression.
The benefits of engaging with insulation manufacturers
When considering ground floor constructions.
Lighting Industry endorses Blueprint for Electrification
The Lighting Industry Association fully supports the ECA Blueprint as a timely, urgent call to action.
BSRIA Sentinel Clerk of Works Training Case Study
Strengthening expertise to enhance service delivery with integrated cutting-edge industry knowledge.
Impact report from the Supply Chain Sustainability School
Free sustainability skills, training and support delivered to thousands of UK companies to help cut carbon.
The Building Safety Forum at the Installershow 2025
With speakers confirmed for 24 June as part of Building Safety Week.
The UK’s largest air pollution campaign.
Future Homes Standard, now includes solar, but what else?
Will the new standard, due to in the Autumn, go far enough in terms of performance ?
BSRIA Briefing: Cleaner Air, Better tomorrow
A look back at issues relating to inside and outside air quality, discussed during the BSRIA briefing in 2023.
Restoring Abbotsford's hothouse
Bringing the writer Walter Scott's garden to life.
Reflections on the spending review with CIAT.
Retired firefighter cycles world to raise Grenfell funds
Leaving on 14 June 2025 Stephen will raise money for youth and schools through the Grenfell Foundation.
Key points for construction at a glance with industry reactions.
Functionality, visibility and sustainability
The simpler approach to specification.