Any time there is a threat of biological or che­mical attack, the first thing you hear about is gas masks.

Gas masks -- more generically known as respirators -- are also an important part of industrial safety on a daily basis. They protect workers against everything from flour dust in a grain elevator to the damaging organic chemicals in paint spray.

In this edition of HowStuffWorks, we will look at the technology behind gas masks so you can understand how they work, and when they won't. ­