Korean Air conducted a special inspection on HEPA (high efficiency particulate air) filters on its aircraft in efforts to maintain safety and cleanliness of cabin air.
According to Korean Air, the airline completed a special inspection on HEPA filters and air circulation systems on its aircraft. Korean Air performed checks on the state of HEPA filters installed in air circulation systems, and changed the HEPA filters that needed replacement. The airline also checked the overall performance of air circulation systems by testing the operation of recirculation fans.
Korean Air has been actively reassuring passengers of a safe in-flight environment during the COVID-19 pandemic. Korean Air maintains the quality of cabin air with HEPA filters and air circulation systems that minimize the spread of viruses.
Airbus also stressed the safety of in-flight environment. According to the leading aircraft manufacturer, aircraft are designed in compliance with all Airworthiness Regulations to provide the highest level of cabin air quality.
■ In-flight HEPA filters remove 99.97% of any viruses and bacteria
HEPA filters installed in aircraft effectively remove nearly 100% of any particulate matter that may be present in the air. Particles larger than 0.3 μm (micrometer) cannot penetrate the close-knit fibers within the filters. Even particles smaller than 0.3 μm are filtered as they stick to the fibers, its process varying with the air flow or velocity. These filters meet the standards set for hospital operating rooms or medical laboratories, filtering nearly all of the microscopic bacteria or viruses in the cabin.
Droplets, known as the medium through which COVID-19 viruses spread, are 5㎛ in size, and aerosol particles are about 1㎛ in size. HEPA filters effectively remove droplets, aerosol particles and COVID-19 viruses that may be present onboard.
The airline regularly exchanges HEPA filters in its aircraft to ensure effective performance. In 2019, the airline spent one billion Korean won (nearly 840,000 U.S. dollars) on exchanging HEPA filters.
■ Air circulation system up and running during flight
Air circulation systems start operating when the airplane is on the ground, when APU (Auxiliary Power Unit) is activated for power supply.
The air circulation system continues to operate during the flight. Aircraft cabin is supplied with a mix of outside air and filtered air, combined with a ratio of 50 to 50.
Outside air at a cruising height is 50 degrees Celsius, with a humidity level below one percent. When fresh air enters the airplane through engines, it is compressed at a high temperature. Next, the air goes through the ozone converter, which removes harmful ozone components. Then the heat exchanger adjusts the air temperature.
The fresh air is then mixed with the HEPA-filtered air before entering the cabin. This process makes it an inhospitable environment for viruses and bacteria to survive.
■ Cabin air flows from the top down, preventing the spread of contaminants
The direction of air flow also plays a crucial role in preventing spread of COVID-19 onboard.
The sterilized air enters the cabin from the vents in the ceiling and exits through the floor, creating a top to bottom flow. Even if virus-containing droplets are ejected into air, they would fall to the floor, instead of onto surrounding seats. This leads to lower probability of virus transmission in the cabin.
Moreover, the air is exchanged every two to three minutes. Generally, the air is exchanged every ten minutes in case of hospitals and every twenty minutes in offices.