Most frequently, your workers will be well protected with N95 disposable respirators, which, as evidenced by their name, reduce about 95 percent of particulates in the air. They are extremely convenient and relatively inexpensive, allowing employers to be sure that no cross contamination is happening. At the end of each day, the staff simply throws out their disposable respirator and picks up a new one in the morning. However, they are not certified for use in filtering dangerous airborne chemicals or toxic fumes - they can only protect your employees from small inhalable debris like sawdust.
However, for extreme environments, it may actually be more cost-effective, or even required by OSHA, for your enterprise to invest in reusable respirators. These are much more heavy duty pieces of equipment and can be used indefinitely. Filtration packs are inserted into the breathing apparatus and are replaced after a certain period of time, or when they have sustained sufficient exposure to chemicals.
These respirators are built for comfort and durability. Some models are also intended for use with oxygen tanks or otherwise supplied air, to protect those in incredibly volatile or low-oxygen environments.
If your employees are exposed to particulate debris or airborne chemicals in your industry, you should consult an expert to determine which type of respirators are best suited to protect them. It is your duty as a manager or business owner to provide a safe and healthy work environment to your staff, and respirators will often play a role in that effort.