A micron gauge is a high-precision tool used by HVAC professionals to measure the level of vacuum in a refrigeration system. During installation, it is necessary to remove all air and moisture from the copper Line Sets before releasing the refrigerant. A standard manifold gauge is not accurate enough for this task, which is why a dedicated micron gauge is used to reach levels below 500 microns. This ensures that the system is completely dehydrated and leak-free, protecting the compressor from internal damage. We emphasize the importance of this step in our Help and installation guides. Failing to reach the proper micron level can lead to acid formation in the oil and a shortened system life. If you are a contractor looking for professional gear, we invite you to Become a Vendor for access to technical support. This tool is the only way to verify that your Ductless Mini Split has been evacuated correctly.