What is RECIRC on Boeing 737? (Recirculation)

The Boeing 737 aircraft, one of the most popular and widely used commercial planes in the world, is equipped with many advanced systems and features that ensure the safety, comfort, and efficiency of its operations. One such feature is recirculation, abbreviated as RECIRC, which plays a crucial role in maintaining a healthy and pleasant cabin environment for both passengers and crew members. In this article, we will dive deep into the concept of recirculation on Boeing 737, exploring its purpose, function, and benefits.

Why is Recirculation Important?

Recirculation is an integral part of the environmental control system (ECS) on the Boeing 737. The main goal of recirculation is to maintain a consistent temperature and air quality inside the cabin. This is achieved by blending fresh air from the outside with a portion of the warm cabin air and recirculating it throughout the aircraft.

Recirculation helps to minimize the energy consumption of the environmental control system by reducing the need to constantly heat or cool the incoming air. By recirculating a portion of the already conditioned cabin air, the ECS can achieve the desired temperature more efficiently, resulting in fuel savings for the airline and a more sustainable operation overall.

Moreover, recirculation also plays a crucial role in improving the air quality within the cabin. The recirculated air passes through highly efficient filters, known as High-Efficiency Particulate Air (HEPA) filters, which are capable of removing up to 99.97% of airborne particles, including dust, pollen, bacteria, and viruses. This helps to create a healthier and safer environment for passengers and crew members, especially during long-haul flights.

How Does Recirculation Work on Boeing 737?

Recirculation on the Boeing 737 involves a series of intricate processes and components that work together seamlessly to achieve its intended purpose. Let’s take a closer look at how recirculation works:

1. Air Extraction: The first step in the recirculation process involves extracting a portion of the cabin air. This air is then directed to the recirculation system for further treatment and mixing with fresh air.

2. Filtration: The extracted cabin air passes through HEPA filters, which remove particles and contaminants, ensuring a high level of air quality before recirculation.

3. Mixing: The filtered cabin air is then blended with fresh air from the outside. This dilutes any residual contaminants and adjusts the temperature to reach the desired level.

4. Distribution: The blended air, now at the optimum temperature and quality, is distributed throughout the cabin via the air distribution system. This ensures a consistent and comfortable environment for the passengers and crew members.

Benefits of Recirculation on Boeing 737

The inclusion of recirculation in the environmental control system of the Boeing 737 brings forth several benefits, both for the airlines and the passengers. Let’s explore some of these advantages:

1. Energy Efficiency: By recirculating a portion of the already conditioned cabin air, the environmental control system reduces the need for excessive heating or cooling of incoming air. This results in significant energy savings for the airline, contributing to a more sustainable operation.

2. Improved Air Quality: The use of HEPA filters in the recirculation process ensures that the cabin air is consistently filtered and free from airborne particles, allergens, and pathogens. This leads to a healthier cabin environment and reduces the risk of airborne illnesses spreading among passengers and crew members.

3. Enhanced Comfort: By maintaining a consistent temperature and air quality, recirculation helps create a comfortable and enjoyable flying experience for passengers. The elimination of temperature fluctuations and the reduction of airborne irritants improve overall passenger satisfaction.

4. Quieter Cabin: The recirculation system also contributes to a quieter cabin environment by reducing the noise generated by the air conditioning units. This allows passengers to have a more peaceful and relaxing journey.


Recirculation, abbreviated as RECIRC, is a vital feature of the environmental control system on the Boeing 737 aircraft. Its purpose is to maintain a consistent temperature and air quality inside the cabin, thereby improving energy efficiency, air filtration, and passenger comfort. By blending fresh air with a portion of the warm cabin air and recirculating it throughout the aircraft, recirculation ensures a pleasant and healthy flying experience for all on board. The inclusion of recirculation in the Boeing 737’s environmental control system is a testament to the continuous advancements in aviation technology, with a focus on safety, comfort, and sustainability.

References: – Boeing. (2021). Boeing 737. Retrieved from https://www.boeing.com/737

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