There exist two classes of respirators: supplied air and air-purifying respirators. Supplied air respirators provide users oxygen from a source that is not the air around them whereas air-purifying respirators simply clean the air around before the users get to inhale it.
Most air purifying respirators require the users to pull in air through a filter to get it cleaned. For this reason, these air-purifying respirators are typically called negative pressure respirators. On the other hand, a positive pressure dust respirator is a powered air-purifying respirator that delivers clean air to its user. That said, below are the common types of negative pressure respirators.
Chemical cartridge respirators
These respirators filter out low vapour and toxic gas concentrations. They are made from activated charcoal, which absorbs inhaled air contaminants. They offer protection for workers in environments with dust, mist, vapour and gases. They are categorised into half and full masks which can be either reusable or disposable.
These are also known as chemical canister respirators. They are quite similar to chemical cartridges but have more chemical absorbents and a higher filtering capacity. Chemical canister respirators only exist with full-face pieces. They cannot be used in environments that pose an immediate danger to your life and health.
Disposable particulate respirators
These respirators are commonly known as dust masks. They protect users from particulate impurities including fumes, dust and mist. They are made from a fibrous material, which traps particles in the air. They should be switched when the user experiences laboured breathing, or the mask loses shape.
Different respirators are suitable for different environments. It is therefore essential to first identify the hazard you aim to protect the user from before getting a respirator. Respirators have different categories designated by letters N, P and R. R and P are oil-resistant respirators while N-series respirators are not. Filtration efficiency is indicated in percentages of 100, 95 and 99 with 100 being the most efficient.