CABIN AIR FILTRATION SYSTEMS - Novel Technological solutions for Commercial Aircraft

Abstract

There is mounting evidence that Volatile Organic Compounds (VOCs) and other aerosolised condensates and vapours related to contamination of breathing air in modern aircraft could have health and safety implications for both the passengers and the air crew. This presentation provides a review of the technologies currently available for aircraft cabin air treatment; disposable carbon adsorbent filters, photocatalytic oxidation, catalytic converters and non-thermal plasma oxidation. It explains the basic principles of each existing technology and then focuses on the Pall Photocatalytic Regenerable Adsorption (PCRA) system. The PCRA system uses a unique combination of adsorbent and catalyst technologies to remove particulate and gaseous contamination from the cabin air supply. I. Introduction his paper focuses on the technologies that can be installed for the treatment of the cabin air supply on commercial and military aircraft. In modern aircraft the air in the cabin is provided by the environmental control system (ECS) which is designed to control the cabin pressure, cabin temperature, maintain air quality and filter/dissipate any particulate matter, smoke and odours that are present in the cabin 1 . In a typical commercial cabin air recirculation system, the air supplied into the cabin consists of approximately 50% outside air from either the engine’s compressor stage (engine ‘bleed air’) or the Auxiliary Power Unit (APU) which is mixed with approximately 50% of filtered, recirculated air. (Note however, that some aircraft designs are now moving to ‘bleed air free’ ECS). Cabin air particulate filters are normally located in the recirculation loop and these are usually rated at 99.99% sodium flame test efficiency or the equivalent 99.97% D.O.P. (Di-Octyl Phthalate) efficiency. In certain cases a lower level of filtration may be in use, but generally there is an option of upgrading to HEPA filtration (equal to or greater than EU grade H13 2 ). Filters manufactured to this ‘true HEPA’ specification provide excellent standards of particulate contaminant removal and control of micro-organisms from the recirculated cabin air 3 . However, some particulate contamination, odour causing compounds and volatile and semi-volatile organic compounds (VOCs and SVOCs) may enter from the outside air system where filtration is not normally provided. In order to provide a safe, healthy and comfortable environment for the passengers and crew, consideration needs to be given to providing adequate purification of both the outside air (‘bleed air’), as well as the recirculated air, for both existing and future aircraft designs.