Mould remediation

With level 2 you would be dealing with quite large areas of mould in several rooms of a house, flat or other occupied premises, which require an organised and coordinated approach to mould remediation.

Mould remediation would be carried out in most cases by operatives with some basic training, or at least an in-house team carefully briefed, ideally having attended dedicated training courses.

The primary concern is to protect occupants, remediation operatives, and any third parties. The careful protection of those liable to be affected by the subject mould needs to be considered before, during and after the mould remediation.

Pre-site remediation

There should be plenty of notice of a clean-up. Occupants or sensitive individuals need to be re-housed. The clean-up area should be unoccupied. This may be all or part of an accommodation unit, depending on the size and configuration of the unit, the rooms affected, etc.

Before the actual mould clean-up, there may be some opening up to assess the extent of the mould colonisation and to firm-up the package of remediation measures. Such exploratory work could present a risk to health where friable material could be disturbed (e.g. asbestos) or mould spores and fungal fragments released. Therefore take care to ensure that no health and safety risk results from it.

Consider organising inspection by an independent consultant before mould is removed.

Site work

Remediation operatives must wear suitable PPE. It is important that workers do not become blasé concerning self-protection. Even though you cannot see spores in the air, they are there and are potentially harmful.

The spread of contamination must be controlled during the clean-up. This is done using 'engineering controls and work practices', outlined in the The IICRC S520 Mold Remediation Standard.

• Engineering controls include:
  • controlled demolition, which minimises dust creation; and
  • vacuum-assisted power tools and air filtration devices close to the work area.
    Air conditioning can spread contamination from area to area, so if possible this should be switched off.
    As noted by Malcolm Richardson in his discussion paper Moulds and Health (unpublished personal paper), care must be taken to avoid redistribution of newly exposed contaminants via ventilation systems – such systems will require decontamination themselves.
• Air pressure control is the creation of negative pressure in the clean-up area, to reduce/prevent air movement outwards from it, preventing the spread of contamination to clean areas. The Institute of Inspection, Cleaning and Restoration Certification (IICRC) recommends the use of HEPA air filtration devices (AFDs), which can be set up to produce positive or negative air systems, or as 'air scrubbers'. Compartmentalisation can be achieved by tightly fitted plastic sheeting.
• Source containment is where a mouldy wall area is covered by plastic film until such time as it can be gradually peeled back during the mould cleaning process. Individual items can also be 'source contained' by encapsulation in plastic and later removed from site. Careful encapsulation reduces the amount of spores becoming suspended in air.
• Source removal is where the source of contamination (e.g. mouldy insulation quilting) is removed. It is sealed in plastic bags and removed for disposal.
• Local containment could be a room or part of a room. The space is sheeted in the same way as you might 'tent' an area to promote effective localised drying. The plastic sheeting enclosure can be simply fixed by duct tape, or sometimes a frame is erected using poles, telescopic struts, timber uprights, etc. Within the tenting, HEPA filtered AFDs can be installed to create a negative pressure differential, to reduce outward spread of contaminated air from the work area.
• Compartmentalisation (also known as full-scale containment) is where the part of the building subject to the mould is isolated from adjacent areas. Failure to properly compartmentalise could result in the mould spreading elsewhere in the building. This method can be used where it is difficult to isolate the contamination at source, or to locally contain it.

Drying

At the same time as mould remediation is in progress, there will often also be dehumidification as part of a drying operation – probably most often when mould has arisen as 'secondary damage' after a flood. The key risk here is the movement of contaminated air from a contaminated to a clean area and this must of course not be allowed to happen.

Mould cleaning

The key item of equipment is the HEPA vacuum unit. A HEPA filter effectively filters 99.97% of particles, down to 0.3 microns. If mould is hoovered up using such equipment, there should be successful containment of spores and fungal fragments.

Mouldy porous materials such as gypsum plasterboards, carpets and insulation are carefully removed from site bagged up in polythene sheeting, to reduce release of spores.

IICRC discourages spraying, wetting or misting mouldy material, as spores could be dispersed by the spray. Where heavy mould is being remediated in conjunction with asbestos removal, then mist spraying may be allowable, with engineering controls. These could include extraction of run-off water and dehumidification.