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Mould and other fungi are naturally occurring through out the world in any outdoor environment.  They help with the decomposition of organic matter and the world would look a lot different if fungi and mould were not around. 

So why do remediation team members wear non-breathable suits, gloves and respirators if mould and fungi are naturally occurring and common in the outdoor environment? 

When mould grows indoors it is confined to an enclosed environment and, as growth continues, indoor concentration levels of mould spores and microbial volatile organic compounds (MVOC’s) can become very high.  

During the remediation process the mould is aggravated due to the remediation techniques and large volumes of spores and mould fragments become airborne.  Inhalation of high concentrations of spores and MVOC’s can lead to a number of respiratory and digestive tract irritations so the wearing respirators with high efficiency particulate and carbon filters removes respiratory exposure for the team. 

To validate the need for the personal protective equipment air samples were taken at the beginning, during and after a mould remediation job.  The job lasted roughly four hours over a single day and the samples were reviewed in the afternoon two days later. The photos of the air samples below show clear justification for the remediation technicians need to wear respiratory PPE during the remediation process and also just how effective remediation can be.

    Sample 1 – Prior to remediation               Sample 2 – During remediation                 Sample 3 – After remediation 

Sample 1 - taken prior to remediation; mould growth has begun on some of the impact sites.

Sample 2 - taken during the remediation; mould growth can be seen at every impact site indicating very high levels of airborne mould due to disturbance during the remediation process.

Sample 3 - taken after the remediation was complete; there is no visible mould growth indicating viable mould had been removed from the area.

In addition to the mould itself, during growth some species of mould release gases called 'microbial volatile organic compounds' (MVOC's).  Some MVOC's can be smelt as a pungent damp/musty odour.  

In high concentrations the MVOC’s produced can cause irritations to the skin and respiratory tract. To protect the remediation team members from absorption of these gases through their skin they wear non-breathable suits and latex (or similar) gloves; active charcoal organic vapour filters on their respirators protect their airway's.  Where MVOC’s are potentially high, full face respirators, rather than half face respirators and safety glasses, are worn for added protection.

When dealing with highly contaminated environments it is Indoor Air Quality Solutions standard practice to bring down the active mould concentrations by sanitising the environment with a hydrogen peroxide vapour prior to starting any remediation work.  The hydrogen peroxide vapour neutralises the active mould growth and kills any mould and fungi prior to the remediation team entering the contaminated area. The sanitisation is also the final step in our remediation process ensuring a complete remediation.


To ensure that the remediation had resolved the mould growth within a mould affect accommodation room the room was left un-occupied for ~ 2 weeks before being returned to service. The room was inspected prior to re-commissioning and a clear pattern of mould regrowth was noted. 

Likely cause(s):          

Removal of visible mould only (failure to remove mould spore) during remediation process resulted in more rapid mould growth than on areas where mould spore and organism fragments had been mechanically removed with HEPA vacuum.  Mould regrowth occurred when surface moisture, due to unresolved dew point problems within the room, came in to contact with the residual mould spore.                                      

Trialled solution:      

HEPA vacuuming of surfaces to remove mould spore and visible mould; treatment of surface with appropriate chemical.


There is considerable documentation regarding mould remediation techniques and the steps required to complete effective remediation.  Significant cost is incurred when highly labour intensive techniques, such as contact remediation using HEPA vacuuming, are used. The necessity of physically removing mould spore and the mould organism, prior to any chemical treatment, is frequently questioned.

Several remediation guidelines suggest that if the mould and associated spores are not removed during remediation the regrowth of the mould occurs more rapidly when appropriate environmental conditions are met.

It is clearly demonstrated that the physical removal of both visible mould and mould spore during the remediation of surfaces within a room significantly delays mould regrowth and, as such, HEPA vacuuming of internal surfaces during the remediation of rooms with significant air or surface mould contamination must be standard practice. 

E.g. smoke alarms, air-conditioning piping, lights, door frames, skirting, cornice, light and electrical switches.


In all rooms at an establish accommodation facility mould growth was observed radiating from places where wall or ceiling panelling joined a secondary item or fixture.

Likely cause(s):         

Warm, humid air from ceiling or wall space ‘leaks’ through gaps into an air-conditioned room.  When the warm, humid air comes into contact with a surface that is below the dew point of the warm air, moisture condenses on the surface.  When mould spore settles on a frequently moist surface mould will grow.  The amount of moisture decreases with distance from the warm air source and, as such, the mould growth diminishes.


Identified gaps between wall/ceiling panels have been sealed, inspection hatches have been fitted with weather taping, identified gaps around wall and ceiling penetrations have also been sealed. 



Once identified, areas that allow ingress of air from ceiling and / or wall cavities must be sealed to create an effective vapour barrier. Building scopes should reflect the requirement to create an effective vapour barrier thereby preventing air ingress from ceiling and wall cavities in to air-conditioned rooms.



Extensive, regular shaped patterns of mould growth (Cladosporium sp.) was noted on the ceilings of a number of rooms within the residence bedrooms, nursery, family room and kitchen. All rooms affected by the mould growth were located on an external wall of the property.  The indoor temperature was 25°c, Relative Humidity was 65%, with dew point of 18°c.


Mould is a symptom of moisture therefore mould growth on a surface indicates that this surface has been damp.  Mould growth in patterns reflects that the moisture is occurring in these same patterns. 

Dew point is the temperature at which water vapour starts to condense out of air that is cooling - for example when warm moisture-laden air contacts a cool surface.  Above the dew point the moisture stays in the air.  At or below the dew point moisture leaves the air and, in buildings, condenses on the cooler surface that the air is contacting.

When insulation is missing from the ceiling the affected ceiling will be warmer during the day and cooler at night as there is no insulation to protect it from temperature extremes.

In this home, where the insulation was missing or in very poor condition and the indoor humidity was high, the surface temperature of the ceiling was below the dew point resulting in condensation on these areas of the ceiling and, as a result, mould growth. 


Missing insulation was replaced in the ceiling to ensure that ceiling surface temperatures were consistent. Surface mould was remediated by one of our specialist mould remediation teams. Indoor humidity was permanently reduced through additional ventilation.

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