Which type of respirator requires the lung to push air through purifying materials?

The type of respirator that requires the lung to push air through purifying materials is the negative-pressure respirator. This device is designed so that the user inhales air, which then passes through filters or other purifying materials to remove contaminants before reaching the lungs. This method creates a negative pressure relative to the external environment, thereby allowing air to be drawn in through the filters as the user breathes.

In contrast, a positive pressure respirator maintains a higher pressure inside the mask than the surrounding atmosphere, which keeps contaminants out and requires a different mechanism of operation. A self-contained breathing apparatus typically has its own air supply and is not reliant on filtering external air, while an air-purifying respirator can refer to a broader category that includes both negative and positive pressure systems based on their operational mechanisms. The key aspect of the negative-pressure respirator is the way it relies on the user's lung capacity to draw air through the purification system.