HospitalityMould remediation
Decontaminating a hotel kitchen after a Category 3 escape of water
Category 3 water from pipework above the ceiling contaminated a hotel kitchen. Surface tests were low, but laboratory microscopy showed mould contamination on the walls and a timber partition. We decontaminated the kitchen and carried out clearance sampling over two working days.
Client and location details are withheld at the client’s request.
What happened
Category 3 water, also called blackwater, escaped from sewage pipework in the ceiling void and ran down into the hotel’s kitchen and food preparation area.
By the time we surveyed, the materials had dried out. But mould had grown while they were wet, and because the room is used to prepare food, every surface had to be dealt with, not just the visibly affected ones.
What our survey found
Our technical survey combined a visual inspection, moisture and humidity readings, on-site surface and air testing, and samples for our laboratory.
- Visible damage. Mould on a timber partition and a section of wall render, water runs on the concrete walls, and staining to the ceiling tiles.
- Moisture. Readings in the subfloor and the concrete and render walls were within dry standards, and relative humidity was below 52%. No drying was needed.
- Surface testing. The highest ATP reading was 65 RLU, within the normal range. A control swab taken outside the kitchen gave similar results.
- Air quality. On-site particle counting showed normal levels of airborne particulates.
The ATP readings were low even on surfaces where mould was visible. So we took three tape-lift samples to measure how much mould was there and identify it. We analysed them in our own laboratory by direct microscopy to ASTM D7658-17.
| Sample | Result | Category |
|---|---|---|
| Wall render | 16 spores/mm² | Moderate growth (10–50) |
| Concrete wall | 151 spores/mm² | High contamination (over 100) |
| Timber partition | 637 spores/mm² | High contamination (over 100) |
Our conclusion was that the mould had become dormant as the materials dried, and that the kitchen had most likely been contaminated with bacteria that had since died. Neither was a reason to leave the surfaces untreated in a food preparation area.
How the works were delivered
- Assess. Technical survey, on-site testing and laboratory analysis, followed by a written scope of works around two weeks later.
- Contain. The kitchen was sealed off from the rest of the building, with a controlled entry point, signage and a HEPA air filtration unit holding the work area under negative pressure. Airborne particulates were monitored inside and outside the work area throughout.
- Decontaminate. All horizontal and floor surfaces were cleaned with an H-class HEPA vacuum. The walls and ceiling were then treated with the two-stage OXID-8/B-RINSE method: OXID-8 applied and left to dwell, surfaces wiped, then B-RINSE applied and left to dry. Containment sheeting and disposable protective equipment went out as contaminated waste, and a SteraMist treatment covered the room, vents and void spaces, including areas outside the containment.
- Verify. On the second day, ATP swabs, tape lifts and an air sample were taken for laboratory analysis. The scope set out that the kitchen would not be signed off until the results were acceptable, with the treatment repeated if they were not.
Working around the hotel
The works were planned for daytime hours to limit noise for guests nearby. All equipment stayed inside the building, and doors and windows were kept closed except to remove waste.
Facing a similar issue?
Tell us about the site and a technical lead will come back to you.