High humidity and mould contamination

Property suffering mould contamination

In today’s article we will be discussing our recent visit to Salisbury. Our client requested our attendance at his dental practice, as it has a history of high humidity and mould contamination. It was our job to make an assessment of the indoor air quality in relation to selected biological contaminants. 

The building is a three storey town building with brick walls and a flat roof. The dental practice operates from the first and second floor of the property. On the first floor there are three dental surgeries, two toilets, a decontamination room, reception/waiting area, a stock room, an office and an electric cupboard. The second floor consists of a further two dental surgeries, waiting room, a cleaners cupboard and a staff room. The building has a long term history of high humidity and mould on the ceilings of several rooms and corridors. None of the staff working in the practice reported suffering any adverse health symptoms which could be attributed to the building environment. 

High humidity and mould contamination

Inspecting the property

We collected spore trap samples using a High flow 1600 sampling pump onto vesta spore trap cassettes. The samples we collected in the occupied areas of the property were dominated by Penicillium/Aspergillus type of spores and undifferentiated spores. The presence of these types of spores are considered allergenic in sensitive individuals. 

Our surveyor conducted a visual inspection and carried out moisture mapping. He begun the inspection in the decontamination room on the first floor. Here he found evidence of condensation in the top corner of the wall in close proximity to a supply fan. The moisture content in the ceiling was checked incase this was the source of the contamination, however the ceiling showed normal moisture levels. Our surveyor believed that the root cause of mould contamination in this room was condensation of water vapour on the cold ceiling surface. Next we inspected surgery three, where our surveyor observed evidence of staining on the ceiling. The roof had previously been repaired (see image below) however this staining appeared afterwards so additional repairs were carried out but these were also ineffective. Therefore it is likely that the water penetrates the roof in a different area. 

High humidty and mould contamination

In the first floor corridor/stairwell and surgery four there was evidence of mould to the ceilings, which was most likely caused by water vapour condensation on the cold ceiling surface. An accumulation of surface water, debris and moss growth on the roof, increases the coldness of the concrete ceiling thus exacerbating the condensation potential in this area. These areas all lack active ventilation and the window is not used for ventilation due to the proximity to a bus stop with high level of noise and fume pollution. The root cause of the contamination is a combination of high humidity, cold concrete surfaces and lack of ventilation in this room.

High humidity and mould contamination

Remediation recommendations

Our surveyor recommended that the extraction and supply fan in the decontamination room is cleaned thoroughly and that the fans are linked with the light units in order to effectively control the humidity levels in the rooms. The ceilings in the decontamination room, surgery four, first floor corridor and the cleaners cupboard should be insulated in order to prevent condensation and subsequent mould contamination. It is also recommended that passive ventilation ports are installed in these areas to increase ventilation in the room. Finally, our surveyor recommended that all the felt joints and lead flashings on the roof above surgery 3 are resealed in order to address the penetrating damp in this area. 

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