A HEPA (High Efficiency Particulate Air) filter provides a very high level of filtration efficiency for particle contaminants of all sizes. As defined by the Institute of Environmental Sciences and Technology, IEST-RP-CC001.3 and MIL-STD-282 Method 102.9.1, a HEPA filter must capture a minimum of 99.97% of contaminants at 0.3 microns in size.

Obviously, a HEPA filter is a critical component of various systems used in specific applications. For instance, the sealed and pressurised cabin of an aircraft will have hundreds of passengers breathing the same air. The passengers may also include a few with an airborne infection. Having the cabin air pass through a HEPA filter before it’s recirculated in the sealed aircraft space will minimise the spread of infection by removing microorganisms.

On the other hand, a public washroom is located in a public area and may or may not have a door. It’s highly likely the door isn’t airtight, and you may be sharing the space with many people, some of whom may carry an infection such as a cold or flu. For a short period of time, you are breathing the same air, which may be contaminated. After washing your hands, you use the hand dryer fitted with a HEPA filter to blow bacteria-free air on to your hands – while you continue to breathe the same air in the washroom.

As you leave the washroom, you pull open the door by the handle, exposing your hands once again to potential germs.

So was the HEPA filter in the hand dryer of any use to you?

A HEPA filter serves its purpose in a closed, controlled environment, such as a pressurised aircraft or other controlled airtight, hermetically sealed environments. That you had HEPA filtered air blowing on your hands doesn’t mean a thing when you have likely been contaminated by the air in the washroom.

In fact, a HEPA filtered hand dryer may, in some cases, be less hygienic than a non HEPA filtered unit.

A HEPA filter has superfine filtration capabilities and can filter out 99.97% of airborne contaminants. The equipment incorporating the HEPA filter will need heavier duty motors to push air through the filters, clogging up the HEPA filter much quicker than a regular filter and reducing its efficiency. When the HEPA filter starts to fill up with contaminants, the air in the washroom being sucked into the contaminated HEPA filter, may in fact be cleaner than the air leaving the contaminated HEPA filter.

Alternatively, the HEPA filter in the washroom’s hand dryer must be changed on a regular basis, which can be a costly exercise.

The only effective filtration mechanism for a washroom or everyday living would be for a person to wear a sealed mask with a built-in HEPA filter to clean the air before it enters their system.

Based on the above, you can decide whether a HEPA filter is a necessary component of a washroom hand dryer.