Loss of Pressure and a Broken Shower in a Hospital Containment
A 4,000-square-foot sprayed-on friable ceiling in an empty hospital wing is under full containment: 40,000 cubic feet, critical barriers over the HVAC and doors, a three-stage decontamination unit (dirty room, shower, clean room), and six HEPA negative-air machines rated 2,000 cfm each, ducted out a window. On the second morning the magnehelic gauge at the far corner reads -0.005 in. w.c. against a specification of -0.02 in. w.c. The shower drain is clogged and the shower has been taped off. Observation from the corridor: a worker leaves the work area, removes his respirator in the dirty room, walks past the taped shower into the clean room, changes into street clothes, and heads to the cafeteria. Another worker carries a bucket of amended water from the clean room into the work area. Debris bags are staged in the dirty room, which is also used for lunch.
1. Compute the air changes per hour and diagnose the pressure deficiency. What must happen before anyone re-enters?
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Capacity check. 6 machines x 2,000 cfm = 12,000 cfm. Containment volume = 4,000 sf x 10 ft = 40,000 cubic feet. 12,000 / 40,000 = 0.3 volume changes per minute, or 18 air changes per hour - far above the 4 ACH minimum usually specified. Capacity is not the problem.
Diagnosis. With that much fan capacity, -0.005 in. w.c. means the air is not moving as designed: loaded HEPA filters, closed blast gates or dampers, a disconnected or crushed flex duct, one or more units off or tripped, open doors or short-circuiting make-up air feeding straight to the exhaust, the building HVAC re-energized, or an uncalibrated/mis-zeroed gauge with kinked tubing. Verify the gauge first (zero it, check the tubing and ports), then walk the exhaust path, then the supply path.
Before re-entry: restore at least -0.02 in. w.c. at the far corner, confirm the exhaust discharges outdoors away from air intakes and that HVAC openings are sealed and off, and document the reading with time and initials. If the target cannot be restored, stop work, add or repair equipment, and re-baseline. Also check that smoke or a thermal tracer confirms directional flow at the barrier, not just one gauge reading.
2. Identify every decontamination and work-practice violation in the observed sequence, and state the correct sequence.
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Violations observed:
- Respirator removed in the dirty room. It comes off last, in the clean room, after showering.
- No shower. A non-functioning shower is a stop-work condition; workers must be able to shower at the end of the shift and before eating, drinking, or smoking.
- No HEPA vacuuming or suit removal before leaving the work area - the worker carried contamination into the dirty room and then through the clean room.
- Contaminated worker passed through the clean room and dressed there, contaminating the clean side and then the corridor.
- Eating in the dirty room and storing debris bags there - no eating, drinking, or smoking in the work area or dirty room, and waste does not stage where people decontaminate.
- Clean-to-dirty traffic: the bucket should move through the decon sequence in the proper direction with clean outer surfaces, not be walked back through the clean room by a dusty worker.
Correct sequence: in the work area, HEPA vacuum the suit and wipe boots while still wearing the respirator; enter the dirty room and remove disposable coveralls and booties, bagging them; keep the respirator on; shower with soap and water (wash hair, hands, face); move to the clean room; remove and dispose of the respirator last; dress in street clothes stored in the clean room. Waste moves out through the dirty side, sealed and labeled.
3. What are the immediate supervisory actions for this shift, and what goes in the project record?
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Stop work in the containment. No one enters until pressure is restored and the decon unit is functional. Fix the shower drain, replace loaded filters, re-secure ducting, re-zero and confirm the gauges, and re-establish critical barriers.
Deal with the affected worker. He exited without showering and went into a clean public area. Have him shower and change, HEPA-vacuum or launder the clothing, and clean the corridor path he used. Document the deviation and determine whether any hospital space needs wiping or sampling. Notify the project monitor and, if the permit or the facility's infection-control plan requires it, the facility and MDE.
Retrain the crew on the decon sequence before restarting: respirator last, shower mandatory, no eating in the work area, no cross-traffic. Verify that coveralls, booties, andvacuum equipment are actually stocked at the dirty room.
Record: the pressure log with the deficiency and correction, equipment service records, the incident report, retraining signatures, and the day's personal and area monitoring. If the deficiency changed exposure conditions, extend sampling to cover the affected period, because the exposure records and the clearance decision both depend on knowing how long the containment was compromised.