High efficiency air filters are available in various types, depending on the application. The most commonly used HEPA filters include:

1. True HEPA Filters - These filters are made according to strict standards set by the US Department of Energy, which requires them to capture at least 99.97% of particles as small as 0.3 microns.

2. HEPA-Type Filters - These filters provide a lower level of filtration efficiency than true HEPA filters. They are often used in portable air cleaners and air purifiers.

3. ULPA Filters - These filters have a higher level of filtration efficiency than HEPA filters, capturing at least 99.9995% of particles as small as 0.12 microns.

4. ASD Filters - These filters are specialized filters used in smoke-filled environments, such as casinos and bars. They are designed to remove smoke and other airborne particles.