The science behind head protection

The structural fire fighter is subjected to many hazards that could cause serious head, face, or neck injuries without the protection of a firefighting helmet. Because the technology of head protection is so advanced and NFPA requirements are so stringent, the incidence of head injury has been relatively controlled. Perhaps the greatest single reason many fire fighter head impact injuries are relatively minor and infrequent is because helmets are almost always worn at all times at the scene. The same tradition and training is not always true for protective hoods and SCBA. That may be one reason why the most common injuries to the head, neck, or face are from burns.

The structural helmet is designed to mitigate the risk of impact (falling objects, glancing blows, etc.), penetration (nails, rebar, glass, etc.), and thermal assault. The helmet must also provide eye or face protection (or both). NFPA-compliant goggles provide eye protection from debris, ash, embers, chemicals, etc. when the SCBA face piece is not engaged (as in overhaul operations). To be considered primary eye protection, goggles must meet ANSI Z87.1-2003. Most face shields do not meet primary eye-protection requirements.

Because of the known hazards, NFPA testing requirements are extremely demanding, resulting in an increasingly higher level of protection afforded by NFPA-complaint headgear. Most fire fighter helmets rely on the combination of three components to provide protection: a hard outer shell, an energy absorption system, and a suspension system. There are, however, some fire fighter helmets on the market that have designed the energy absorption system right into the suspension system and an outer shell so durable and resistant to impact that no extra energy absorption components are needed. The hard outer shell provides protection against penetration from sharp objects. It also helps dissipate the energy from a falling object by deflecting the blow, as well as by spreading the load of the blow over a large surface area. The energy absorption system provides impact protection by further dissipating any energy of transmitted force through the shell. Finally, the suspension system is made up of a series of straps anchored into the helmet. When a blow occurs to the top of the head, the force that would ordinarily be transferred to the fire fighter’s head and neck is absorbed by the stretching action of the suspension straps. The best level of protection from head injuries on the fireground, however, is when each component works together as a cohesive system.

Editor’s note: This is the first in a five-part look at the science behind head protection.