About Air Circulation in Airplanes

1. Overview

The aircraft always takes in outside air and simultaneously circulates the air inside the aircraft through a high-performance particulate filter (HEPA filter *1). It takes about two to three minutes for air to travel throughout the entire cabin and perform a complete circulation cycle. We call this recirculation system.

2. Recirculation System Method

Highly pressurized hot air travels through air ducts in the wings to an air conditioner located in the lower part of the aircraft (near the underbelly) *2, where it is adjusted to an appropriate temperature and supplied to the cabin.

Each cabin is also equipped with a circulation system that purifies air by passing it through a high-performance particulate filter (HEPA filter).

This system allows for a high volume of outside air to constantly be fed into the cabin, while the air currently circulating in the cabin is kept clean and sterile through the use of HEPA filters.
All aircraft operated by the ANA Group are equipped with HEPA filters.

  1. *1. The High-Efficiency Particulate Air (HEPA) Filter is able to filter particles as small as 0.3 μm in size, meaning that it is capable of removing more than 99.97% of all airborne particles.
  2. *2. The Boeing 787 draws outside air directly into its air-conditioning system from below the cabin, rather than from the engine.

Image 1: Air circulation throughout the cabin

Image 2: Flow of the air using HEPA filter