... ) 3.1 .First class: chemical agent: Hydrocyanic acid, cyanogens chloride, arsine, phosgene, chloropicrin, bromomethane, lewisite gas, mustard gas, sarin, vx gas, toxic ... weight :21kg 4.Usage maintenance and maintain4.1.The selection of gas mask 4.1.1. checking the position between glasses and eyes ... right selection. 4.2.The procedure of wearing gas mask 4.2.1. adjusting the position of fillets 4.2.2 ...