Door Propped Open: Containment Failures You Can See From the Entry
Your crew of four is on day two of interior abatement in a vacant third-floor apartment of a 1926 building: six door casings, four window units, and about 200 sq ft of baseboard. The building has central HVAC with a return register in every apartment. Containment is 12 ft by 15 ft with an 8-ft ceiling; floors carry one layer of 2-mil poly, walls one layer, and a single HEPA negative-air unit rated 1,000 CFM exhausts through a window. Decontamination is a spray-and-wipe station in the entry. You arrive at 10 a.m. and find the apartment door propped open, no barrier over the HVAC return, a smoke tube showing no draft at the entry, one worker eating a sandwich on the clean side of the poly, and a loaded debris bag sitting in the public hallway.
1. Rank the deficiencies you can see and state what happens in the next 30 minutes.
Read the worked answer
The call: Stop production. The containment has already failed and dust is moving through a shared building.
Ranking and actions:
- Open door and debris bag in the public hallway - active release to a common area. Move the bag back inside or into a sealed container, HEPA vacuum and wet wipe the hallway path, close and seal the door. Highest priority because non-workers are being exposed.
- Missing critical barrier on the HVAC return - the central system can distribute lead dust to every apartment in the building. Seal the return and supply registers with poly and tape before anything else is disturbed.
- No verified negative pressure - the containment may be neutral or positive. Install a manometer or use the smoke tube properly at the entry; if no sustained inward draft at 0.02 in. w.c. or better, find the leak (window duct seal, poly seams, ceiling penetrations) before work resumes.
- Eating on the clean side - ingestion route, and it tells you the crew does not understand the decon sequence. Retrain on the spot and re-establish a real three-stage decon.
Document the stop-work, the corrections, and the notification to the general contractor.
2. The negative-air unit is rated 1,000 CFM for a containment of about 1,440 cubic feet. Is capacity your problem? Show the reasoning.
Read the worked answer
The call: Capacity is not the problem; the envelope is.
Reasoning:
- Containment volume is roughly 12 × 15 × 8 = 1,440 ft³. At a typical target of about 6 air changes per hour, you need about 1,440 × 6 = 8,640 ft³/hr, or about 144 CFM.
- Even derated heavily for filter loading and duct losses, a 1,000-CFM machine is far more than that. Adding machines will not fix a propped door and an unsealed return - it will just pull more building air, and possibly pull dust toward the wrong rooms.
- What to check instead: is the machine running and is the HEPA filter properly seated; is exhaust going outdoors and not into another unit, a stairwell, or a walkway; is the window duct sealed; is the pressure differential actually being measured and logged; is a backup unit on site; and is the machine oversized enough to suck the poly off the walls or to backdraft the HVAC once the return is sealed.
- Record the pressure readings at the start and end of each shift.
3. The general contractor says, "Finish today, we'll clean the hallway tomorrow." How do you respond, and what gets written down?
Read the worked answer
The call: Refuse, and put the refusal and the reason in writing the same day.
Reasoning:
- Work does not resume until the door is sealed, the registers are critical-barriered, and negative pressure is verified. Finishing first and cleaning later means generating more dust into a space that is already contaminated.
- The hallway gets HEPA vacuuming followed by wet wiping now, not tomorrow, because it is a common area and building occupants use it.
- Write it down: the stop-work in the daily log with times, the deficiencies found, the corrections made, the pressure readings, the retraining of the worker who was eating, and a written notice to the general contractor stating that work was halted for containment failure and what is required to resume.
- Expect clearance to be extended to the hallway and adjacent surfaces if the release was significant. If you cannot show what you did and when, you will own all of it.