In HVAC (Heating, Ventilation, and Air Conditioning) systems, "outside air" and "makeup air" are terms used to describe two different sources of fresh air introduced into a building. While both serve the purpose of supplying fresh air, they differ in their intended applications and where they are introduced in the system.
- Outside Air: Outside air refers to fresh air that is brought into a building from the external environment. It is typically drawn from the outdoors and introduced into the HVAC system to provide ventilation and improve indoor air quality. Outside air is necessary to dilute indoor pollutants, remove odors, and replenish oxygen levels. The amount of outside air brought into the building is usually determined based on building codes, ventilation standards, and occupant requirements.
Outside air is typically introduced through ventilation systems, such as intake louvers, dampers, or dedicated outside air units. It is then conditioned (heated or cooled) and distributed throughout the building along with the recirculated air from the return air system.
- Makeup Air: Makeup air, on the other hand, is a specific type of outside air that is introduced into the building to compensate for the air that is exhausted from the building due to various processes or ventilation systems. It "makes up" for the air being removed from the building, preventing negative pressure situations that can cause problems like backdrafting in combustion appliances or difficulty in opening doors.
Makeup air is commonly used in commercial and industrial settings, such as restaurants, kitchens, manufacturing facilities, and paint booths. These spaces often have exhaust systems to remove heat, smoke, fumes, or moisture. Without proper makeup air, negative pressure can occur, leading to airflow issues and potential hazards.
Makeup air is typically introduced close to or in the vicinity of the exhaust points to ensure a balance between the air leaving and entering the building.
In summary, the main difference between outside air and makeup air in HVAC systems is their purpose and where they are introduced:
Outside air is fresh air drawn from the outdoors and introduced to improve indoor air quality and provide ventilation throughout the building.
Makeup air is a specific type of outside air introduced to compensate for the air being exhausted from the building due to ventilation systems or various processes, maintaining a balanced air pressure and preventing negative pressure situations.