24 Policemen use the masks for what reason?
why do policemen wear a mask while regulating traffic in a crowed area
Statement I: Policemen regulating traffic at a crowded crossing often wear a mask.
Statement II: Mask filters carbon dioxide and sends pure oxygen inside.
which substance is used for adsorption in gas masks used in coal mines?
What is the role of activated charcoal in gas masks used in coal mines?