Fireproofing,a passive fire protection measure, refers to the act of making materials or structures more resistant to fire, or to those materials themselves, or the act of applying such materials. Applying a certification listed fireproofing system to certain structures allows these to have a fire-resistance rating. The term fireproof does not necessarily mean that an item cannot ever burn, it relates to measured performance under specific conditions of testing and evaluation. Fireproofing does not allow treated items to be entirely unaffected by any fire, as conventional materials are not immune to the effects of fire at a sufficient intensity and/or duration.
Passive Fire Protection measures are intended to contain a fire in the fire compartment of origin, thus limiting the spread of fire and smoke for a limited period of time, as determined the local building code and fire code. Passive fire protection measures, such as steel structures , fire stops, fire walls, and fire doors, are tested to determine the fire resistance rating of the final assembly, usually expressed in terms of hours of fire resistance (e.g. 30 mins,60 mins, 90 mins,120 mins). A certification listing provides the limitations of the rating.
An Intumescent is a substance that swells as a result of heat exposure, thus increasing in volume and decreasing in density. Intumescent are typically used in passive fire protection.
As the name suggests, passive fire protection (PFP) remains silent in your coating system till the eventuality of a fire.
There are mainly two types of PFP:
a) Vermiculite fire protection
b) Intumescent fire protection
vermiculite fire protection, the structural steel members are covered with vermiculite materials, mostly a very thick layer. This is a cheaper option as compared to an Intumescent one, but is very crude and aesthetically unpleasant. Moreover if the environment is corrosive in nature, then the vermiculite option is not advisable, as there is the possibility of water seeping into it (because of the porous nature of vermiculite), and there it is difficult to monitor for corrosion.
Intumescent fireproofing is a layer of paint which is applied along with the coating system on the structural steel members. The thickness of this Intumescent coating is dependent on the steel section used. For calculation of DFT (dry film thickness) a factor calledHp/A(heated perimeter divided by cross sectional area), referred to as "section factor" and expressed in m-1, is used. Intumescent coatings are applied as an intermediate coat in a coating system (primer, intermediate, and top/finish coat). Because of the relatively low thickness of this Intumescent coating (usually in the 350- to 700-micrometer range),nice finish, and anti-corrosive nature, Intumescent coatings are preferred aesthetically and performance-wise.
It should be noted that in the eventuality of a fire, the steel structure will eventually collapse once the steel attains the critical core temperature (around 550 degrees Celsius or 850 degrees Fahrenheit). The PFP system will only delay this by creating a layer of char between the steel and fire. Depending upon the requirement, PFP systems can provide fire ratings in excess of 120 minutes. PFP systems are highly recommended in infrastructure projects as they can save lives and property.