Technician A says a respirator will block all poisonous fumes produced in a shop. Technician B says a respirator will block only those fumes for which it is rated. Who is right?

Technician B

Explanation:

There's no such thing as a perfect filter available to block any kind of toxic fumes. The effectiveness of a filter depends of various things, such as the air flow and the particles size. They have specific rates depending on the place they are designed to be installed on, so they have to be chosen with that in mind. For example, most industrial applications have more demanding restrinctions than a commercial one, so a filter designed for the latter would probably not be useful for the first case.