With the fire season approaching and interagency aviation operations gearing up, the U.S. Department of the Interior (DOI) and the U.S. Forest Service (USFS) this week issued an accident prevention bulletin reminding helicopter flight crews to ensure their helmets meet interagency guidelines and, more importantly, offer adequate protection.

The bulletin warns that some helmets may contain outdated components that don’t offer the same level of safety as updated parts, and that some helmet manufacturers may misrepresent the level of safety their products provide. It also warns that helmets designed for use in fixed-wing aircraft, “do not provide adequate protection for helicopter occupants and are not approved for helicopter use.”

The bulletin cites U.S. Army research that shows 30% of the most severe impacts occurred on the sides of the helmet, with injuries — including skull fractures — resulting from non-energy-absorbing ear cups. And it includes best practices for caring for protective equipment like helmets.