There is a lot of hype on social media about how to kill mould that is completely unfounded, so I want to set the record straight in relation to the use of bleach, ozone and essential oils and their impact on mould. Bleach is ineffective in killing fungi (however, it is effective against bacteria), because it is highly alkaline and may provide the microbes in a water-damaged building with a food source. Furthermore, it only ‘bleaches’ the mould until such time that the melanin compounds in the hyphae (the branching filamentous cells of the fungus) recover and, voila, within weeks the mould becomes visible again. Similarly, ozone should NEVER be used in a water-damaged building because it is an eye, nose and lung irritant; it is ineffective at killing mould spores; it reacts with numerous volatile organic compounds in a water-damaged building to create more toxic chemicals; it may degrade the colours of surfaces such as paintings; and lastly, it is very reactive with synthetic materials such as plastics, nylon and the rubber backing on carpets and curtains. For these reasons, the US Environmental Protection Agency has issued warnings against using ozone inside a building. Whilst several studies have confirmed that tea tree and clove essential oils are remarkably effective antifungal agents, they should be used sparingly (or not at all) in mould remediation jobs because the amount required can be toxic to children and to chemically sensitive individuals. Furthermore, killing mould is irrelevant when most spores are already ‘dead’ (can’t germinate) but may still cause harm when they are inhaled.

The best way to deal with mould is to physically remove it. This can be achieved by conducting a HEPA sandwich which involves vacuuming the affected non-porous surface using a vacuum cleaner fitted with a HEPA filter, then wiping with a damp microfibre cloth, and vacuuming again. The microfibre cloth should be soaked in ½ litre of water to which a generous squirt of dishwashing liquid has been added. This procedure will remove the biofilm that microbes in a water-damaged building feed on. The cloths should then be rinsed thoroughly before reusing. At the end of the job, the cloths should be discarded along with the HEPA filter and disposable vacuum cleaner bag. For a detailed discussion on how to remove visible mould from porous (soft furnishings, unsealed timber, rugs…) and non-porous surfaces (hard timber, glass, metal, plastic, concrete…), or a checklist on what your mould remediator should do when remediating your home, buy my book Healthy Home Healthy Family.