Two technicians in protective suits and respirators at a plastic containment wall. A representative photo of the task, not a record of work at any particular property.
The idea in plain terms
Cutting moldy drywall or brushing contaminated wood throws spores and fragments into the air. Containment wraps the work zone in polyethylene sheeting so that dust has nowhere to go but into a filter. A negative air machine, essentially a fan with a HEPA filter, pulls air out of the enclosure and exhausts it, usually outside through a window or duct. Because more air leaves the enclosure than enters, air leaks flow inward through any gap instead of outward.
You can see this working: the plastic walls bow gently inward, and a zipper door pulls toward the work area when opened a little. If the sheeting is billowing out toward the hallway, the pressure is wrong.
The setup changes with the space. In a crawlspace, the hatch and every floor penetration above it become the boundary, and the air machine often vents out a foundation vent. In a finished basement, a room or a corner is walled off floor to ceiling. A small job inside one wall cavity may need only a mini enclosure around the cut, but it still needs filtered exhaust.
Words you will hear on the first day
- Poly
- Polyethylene plastic sheeting used for containment walls, floor protection and covering openings.
- Zipper door
- An adhesive zipper applied to the sheeting so workers can enter without opening a large gap.
- Air scrubber
- A portable HEPA filtration unit. When ducted to exhaust outside the enclosure it creates negative pressure.
- Decon chamber
- A small plastic room at the entrance where workers remove or HEPA vacuum protective clothing before leaving.
- Manometer
- A gauge that measures the pressure difference between inside and outside the containment.
What to check before removal begins
- Sheeting is sealed to walls, floor and ceiling with no loose edges
- HVAC registers and returns inside the area are sealed off, and the system plan is explained
- The air machine exhausts outside the house or outside the containment, not into another room
- The plastic pulls slightly inward
- There is a defined path for carrying bagged debris out
- Floors along that path are protected
Proper setup versus a shortcut
Proper
- Full enclosure sized to the work
- Negative pressure that you can see
- Debris bagged inside and wiped before leaving
- HVAC isolated for the duration
Shortcut
- A single sheet hung over a doorway
- Box fans blowing out a window with no filter
- Open bags carried through the house
- Furnace running and pulling air from the area
General information for Wheat Ridge, not a quote or professional advice. In an emergency, call 911.