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What is the Difference Between an AMU & an MUA?

Maintaining good indoor air quality and balanced air pressure is essential for a safe and healthy working environment in any shop. When you operate a paint booth in your shop, it can create problems with indoor air pressure and quality if you do not take precautions. This is especially true in smaller areas where the pressure changes caused by a paint booth can quickly affect the air in the entire building.

Fortunately, there are two ways to maintain good air quality and proper air pressure: providing make-up air (MUA) to the shop or adding an air makeup unit (AMU) to the paint booth. Understanding the operational differences in these solutions as well as the potential benefits can help you determine which option is right for you.

Paint Booth Operation Causes Negative Air Pressure

During paint booth operation, air is exhausted from the booth. While it is necessary to exhaust air in order to exhaust the overspray from painting, this process can quickly change the volume of air in the booth, causing negative air pressure to develop.

There are several problems that negative air pressure can cause:

  • A vacuum effect that pulls dirt and debris into the paint booth
  • Uneven curing of the finish on painted items
  • Poor indoor air quality
  • Drafts and temperature fluctuations
  • Suction that makes the doors and windows hard to open

To restore balanced air pressure inside the booth, air must be added back in to replace the air that is exhausted.

Make-Up Air Balances Shop Air Pressure

To make up the air pressure inside the paint booth, you need to pull in new air to replace the exhausted air. In some setups, a booth will replace exhausted air by drawing in air directly from the shop’s interior atmosphere. However, pulling the shop’s air into the booth can cause changes to the pressure of the shop at large. In a small building, normal paint booth operations can quickly lead to negative air pressure in the entire shop.

Make-up air (MUA) is intended to replace the air from the shop that is used and exhausted by the paint booth. MUA solutions sometimes function as part of the HVAC system to draw replacement air from the outside. It could also function without a HVAC system to push air into the building. This extra ventilation restores air pressure and improves the overall quality of air inside the shop.

An Air Makeup Unit Provides Additional Benefits

A more popular option is an air makeup unit (AMU) which balances air pressure and improves air quality by providing replacement air into the booth itself. An AMU is designed to provide the right amount of air into the paint booth to balance the volume of air exhausted.

Many AMU models offer the ability to heat the air for a temperature-controlled spraying environment. The heating feature allows the AMU to be put into “cure” mode. When in this mode, the paint is cured (or baked) at a very high temperature and is done in less than an hour. This feature increases the production capacity of any shop.

  • Providing replacement air directly into the booth eliminates negative air pressure in the shop
  • AMUs can reduce the amount of dust and other particles that can ruin the paint finish
  • Temperature-controlled air can reduce the time it takes for a finish to cure, especially in colder environments

In large shops that have more than one paint booth, installing AMUs for each booth provides more functionality than simply getting a single MUA solution for the shop itself.

Deciding Between an AMU and an MUA Solution

Paint booth operation creates air movement due to exhaust, and that air must be replaced to avoid issues caused by negative air pressure. A MUA shop solution provides replacement air to the interior of a shop, improving ventilation and reducing air pressure problems. An AMU provides air within the paint booth itself to balance the air pressure. Heated AMUs control the temperature inside the booth with warm air and can run cure cycles that ensure faster, consistent curing.

Standard Tools designs and builds the Sure-Cure AMU and MUA for these different air replacement circumstances. The units are built to a shop’s specific gas and power, CFM requirements and installation prerequisites. Although Standard Tools is a paint booth manufacturer, the Sure-Cure AMU can be built to be compatible with any brand paint booth. All of our air-replacement solutions improve the air quality and production level of a shop. Contact an expert at Standard Tools to get more information on the Sure-Cure AMU and MUA. The team can help you figure out which solution is best for your shop.


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