Headgear tends to sit in 3 categories.
-full-face masks, such as or tactical helm. These are worn on the ‘normal’ layer, and are usually highly encumbering, and only 1 can be worn at a time.
-Standard helmets. Motorcycle helmets, firefighters helmet, lobster helm, bicycle helm, newsboy cap or the infamous pot helm. These still occupy the normal layer, and only 1 of these can be worn at a time.
-Small, cloth headpieces, such as turbans, cotton hats, knit hats, balaclavas, rioter masks, or guy-fawkes mask. Several of these could be worn at once, and their primary purpose is heat, utility, or to augument the helmet’s protection.
Im not familiar with the exact stats of the sercurity helm, but it sounds mid-high tier.