Chemsuits are sealed outfits that protect the user from hazardous environments. In Pelvanida, they were located in various emergency stations along with other equipment such as gasmasks, fire axes, and first aid kits.
They were the only known protection from the bio-bomb in the anti-matter universe. James, Ender McThair, and Ken survived the initial falllout because terrorists had previously forced them to wear chemsuits. Later, Neku obtained chemsuits from Crimson Base, and they proved instrumental in his team's survival. (Ground One)