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A motorocycle helmet is not fire rated. It won't resist fire. It's not required of an mc helmet because you don't get trapped "inside" in a motorcycle accident like you can in an auto accident.
Motorcycle helmets are usually okay with most groups for "hot laps," HPDE, Driver's School, Time Trial, etc... as long as they are current rating, i.e. not too old. But mc helmets are not approved for wheel to wheel racing.
Bottom line is that you need to check with the organization with which you're planning on participating.
(Fire rating means a helmet or other protective article of clothing is made from materials that resist heat and open fire for a minimum number of seconds to help protect you and give you time to get out, or be pulled out, of the vehicle. A higher number means longer protection, in seconds.)
Happy motoring!