Why Do We Use HEPA Filters and Negative Pressure?

6/1/2022 | Michael D. Vinick, ASCS, CVI, President - Duct & Vent Cleaning of America, Inc., Past President - NADCA

HEPA stands for High Efficiency Particulate Arrestance (HEPA). HEPA filters are 99.97% effective in capturing particulate matter that is as small as .3 micron in size. To give you a bearing on this, 1 micron equals 1 in 25,400 of an inch. An average human hair may be able to be seen at 75 microns. We use HEPA Filtered Vacuums when air duct cleaning to ensure that we are capturing particulate build up in the HVAC system from escaping into the building space, which can be considered an occupied space.
Filters are measured in MERV (Minimum Efficiency Reporting Values). The higher the MERV rating, the better the filter is at trapping smaller particles. MERV ratings can rate a filter for particles up to 10 microns in size. Obviously not all filters are created equal and not all filters are designed for the purposes of cleaning ductwork.
Our approach of maintaining negative pressure on the ductwork within the area of a HVAC system that we are cleaning, ensures that we capture the particulate that we are removing from the ductwork at the site of the built-up debris. Depending upon the accessibility of the ductwork, we either remove the particulate from the point of buildup, or we agitate the particulate and remove it at the nearest location we can access the ductwork with our HEPA filtered vacuum.
These key elements of our duct cleaning process are integral in ensuring we can clean the ductwork appropriately and at the same time maintain a safe space. All our cleaning methodologies adhere to NADCA Standard 2021 for Assessment Cleaning and Restoration of HVAC Systems.

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