What Is Negative Air Pressure in Mold Containment?

A mold professional sets up a plastic containment barrier around the affected area. This creates a sealed environment to isolate the mold growth. A powerful HEPA-filtered air scrubber is then placed inside this enclosure and vented to the outdoors through a window or door.

The air scrubber exhausts air from inside the containment to the outside. This removal of air lowers the air pressure inside the plastic sheeting compared to the rest of your home. Because air naturally flows from high-pressure to low-pressure areas, any small gaps in the barrier will suck clean air in, rather than letting contaminated air escape.

The primary tool for creating negative pressure is an air scrubber, also known as a negative air machine. This is a portable unit containing a high-efficiency particulate air (HEPA) filter. The fan pulls air through this filter, which captures at least 99.97% of particles, including mold spores, before exhausting the cleaned air.

Heavy-duty plastic sheeting and durable tape are used to construct the containment chamber. A manometer, or pressure gauge, is often used to monitor the pressure difference. This device confirms that the containment is effectively sealed and maintaining the correct negative pressure throughout the job.

• Air Scrubber with HEPA Filter
• Heavy Mil Plastic Sheeting
• Zipper Doors for Access
• Duct Tape and Sealing Tape
• Flexible Exhaust Ducting
• Pressure Monitoring Gauge

If you hire a mold remediation professional, you will see them set up a plastic containment zone. They will seal off doorways, vents, and other openings. You will hear the constant hum of the air scrubber running for the duration of the project.

You should stay out of the work area entirely. The pros will use the zippered door to enter and exit, and they may wear protective suits and respirators. After the mold is removed and the area is dry and clean, they will take down the containment and perform final air testing to verify the space is safe.