A: Intumescent means "swelling and charring when exposed to flame". When exposed to fire, the coating will rapidly react, becoming a compact foam, dense carbon char, or similar, to stop fire migration.
Intumescent Paint products must have an MEA (Materials and Equipment Acceptance) Number to qualify as an approved means of rating structural members. The paint must be applied and utilized in a manner consistent with the MEA Approval.
MEA Numbers for Intumescent Paint may be verified by lookup on the Department of Building Website. Check the MEA Index, and search under the "Fire Protection" heading to find approved Intumescent Paints and their respective MEA Numbers and MEA Approval documents.
The MEA Number must be listed on the DOB Drawings and Construction Documents when filing for approval and permit.
Here is a sample MEA-Approval for an Intumescent Paint product.