NOTE: This article has been updated. It was originally published on September 21, 2019.

As the topic of cabin air quality has garnered more and more attention over the years, it is becoming essential for airlines and operators to be aware of their options.

Advancements in aircraft cabin air filtration have come a long way since it was introduced in the 1980s. Long gone are the "smoking on the plane" days, and transient or nuisance odours can now insight anything from passenger complaints to litigious claims from the flight crew.

Much can be done, though, by upgrading an aircraft's filters. In this article, we will look at the various types of filtration that are available on the market.

Our Pall filter parts that meet EASA's safety guidance

Type	A320 Family	A330 Family	A380 Family	737/757 Family	777 Family
Standard HEPA	QA06423-01	QB0408-01	QB0754-00 QB0757-00 QB0919-01	CD01068F4	CD00944F3
Advanced Carbon HEPA	QB0654-01 QB0654-02 QB0654-03	QB0434-02	n/a	QB05154-01 QB05154-02	CE01311F1

HEPA Filters

High-efficiency particulate air (HEPA) technology has been around since the 1930s and was officially commercialised in the 1950s. Pall Aerospace was the first company to implement these hospital-grade HEPA filters for commercial aircraft in the 1990s.

While HEPA is still highly effective for filtering out bacteria, viruses, fungi and particulates in recirculated cabin-air, it is essential to be aware of some factors and limitations.

True-HEPA

This term refers to HEPA filters that conform to and satisfy specific industry standards of efficiency, enforced by agencies like the U.S. Department of Energy and the European Union.

According to a briefing paper issued by IATA, HEPA (or True-HEPA) is classified as being able to filter out 99.97% of all harmful or odour-inducing particulates 0.3 microns in size.

HEPA Type

These are essentially commercial HEPA knock-offs that don't adhere to the same efficiency standards–with efficiency ratings as low as 80%, in some cases.

In our research, we were unable to find any aviation aftermarket filters with the classification of HEPA-Type. This does not mean that they do not exist, and operators should be aware that HEPA-Type filters do not meet aviation standards.

HPAC (Highly Activated Carbon Filters)

Where HEPA filters may come up short is in their ability to filter out noxious odours, activated carbon fills in the gaps. Activated Carbon Filters function by increasing the surface area of a base carbon filter, essentially creating additional pores within its carbon structure. Contaminants adhere to these "pores" and lock them in the filter.

"Activated carbon has been proven to be the most economically efficient means of removing odours from the air. Anything in the cabin that emits an odour can contribute to cabin odours in the recirculated air," says John Vinson, Pall Product Manager, Americas at Satair.

Pall PUREair A-CAF

Pall Corporation, the global leader of advanced filtration, separation and purification technologies and the brand responsible for first introducing medical-grade HEPA filters into the aviation industry, has developed a proprietary filter technology called A-CAF (Advanced Cabin Air Filters).

A-CAF filters combine True-HEPA filtration to remove microbial, bacterial and viral contaminants. The technology, in use, has been said to improve cabin air quality by 30%.

The A-CAF product lines are FAA-PMA approved and can replace standard HEPA filters in both Airbus and Boeing models.

*cover image courtesy of Pall Aerospace

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How to ensure that your aircraft has the most effective cabin air filters