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In light of the recent flooding in QLD and NSW, we asked Erin Anderson — a Microbiologist and Biotechnologist at EvaScientific — how to best clean mould.
Remember that mould exposure can cause health problems. Particularly for people with asthma or allergies. Both the dead and living parts or mould can be hazardous. Always use PPE and, if possible, wait until conditions are less humid and damp.
In addition, if a surface is contaminated with mould, it is important to consider the structural integrity of the affected material and any other associated hazards (e.g. bacteria and viruses in flood water).
Ventilate the area by opening windows (if it is dry outside), using fans, or using a dehumidifier. Dispose of any affected soft furnishings, carpets and porous materials. If possible, on a dry day, move items out into the sun for a few hours.
Sometimes a mould problem can be treated by addressing the underlying cause of moisture, treating the moisture problem and removing the fungal material from the affected surface.
Use a mild, phosphate free detergent to physically clean the fungal material from affected surfaces.It is important to avoid using cleaners that leave inactive residues on the surface. Such as cleaning solutions that contain phosphates or oils (including essential oils).
Make sure that surfaces that are cleaned, dry quickly. If cleaning is occurring in conditions that remain very humid or damp, it may be necessary to avoid the use of a water-based cleaner and instead use an alcohol-based cleaner. Alcohol-based cleaners will dry faster.
If a surface is heavily contaminated with mould and the above processes do not work. It may be necessary to treat the surface with a disinfectant.
When choosing to treat a surface. It is important to use a cleaner that is effective. Using an ineffective cleaning approach can add more moisture and even leave behind nutrients for more mould to grow.
When it comes to disinfectants, not all products are tested on mould. Many are not particularly effective at killing mould. No cleaning product is 100% effective at killing mould spores.
In general, the most readily available and proven disinfectant for the treatment of mould is bleach. In Australia, cleaning products that contain an effective bleach concentration should be labelled as a ‘disinfectant’ and will list the active ingredient ‘sodium hypochlorite’ on the front label. Peroxide cleaners can also be effective.
As always, ensure you read the label before using any cleaning chemicals, consider the safety hazards and follow the directions. Both bleach and peroxide-based cleaners will discolour some surfaces.
As mentioned above, the most important step is to treat the moisture problem. Mould spores (the reproductive particle of moulds) are always present in the air in both indoor and outdoor environments. Mould will return, even to clean surfaces, wherever there is moisture or humidity.
While most would agree it is beneficial to avoid hazardous chemicals wherever possible. It is also important to remember the health hazards of ineffective management of mould. While the two cleaning solutions discussed below are frequently recommended, it is important to consider the need to balance the safety hazards in context when choosing an approach.
The efficacy of vinegar has not been substantiated sufficiently to recommend use on heavily contaminated surfaces. Particularly in conditions where the addition of the water component of a vinegar solution could further contribute to a moisture problem. Vinegar does not function as a surfactant and will not assist with the physical removal of fungal material from a surface. Hence, the use of a mild phosphate free detergent is recommended above instead of vinegar.
Essential oils, such as clove, thyme and cinnamon have been shown to have some anti-fungal properties. However, this is an initial effect. Once the volatile component of the essential oil evaporates, an oil residue is left on the surface. This leaves behind nutrients which mould can use to grow. Also, importantly, the safety hazards of some essential oils should be equally considered. In particular, any skin contact hazards.
The reality is that cleaning chemical companies are always looking for new and effective cleaning solutions. Scientific papers around the efficacy of both vinegar and essential oils have been published and are publicly available. So, if vinegar or essential oils were effective enough on their own to pass laboratory testing standards as a ‘mould killer’ — they would be sold, in a bottle labelled as such.
© Erin Anderson. Notes are non-specific and should not be considered individual professional advice.
