The Nine Steps to Eliminate Mould Naturally

Hitting Home

On February 28, 2022 we heard news that our family home in Lismore Australia had been swamped in a catastrophic flood. Within a few days, we were camped up in a caravan in the front yard of the ruined house. We spent several months renovating the house and helping others overcome problems such as persistent mould.

ozone generator

Given our expertise with ozone, many people were asking for advice of how to best integrate their air ozone generator into their mould reduction program.

This nine step guide is a result of our own research and personal experience and should not be taken as personal professional advice.


What is mould?

Mould is a member of the fungi family which also includes mushrooms and yeast. It can be found almost everywhere on earth and is a vital part of our eco-system, helping to break down organic matter among other tasks.

How does mould grow?

Mould needs three conditions to thrive; moisture, food source and protection from sunlight and moving air. Unfortunately, many materials that we have in our homes such as plasterboard, wood, soft furnishings etc provide an ideal environment for mould growth if moisture is present.

How does mould reproduce?

Mould reproduces by means of tiny spores, which are similar to the seeds of plants. Their small size means that they can travel long distances on the wind or on clothing. They can survive in environments not suitable for normal mould, which means that while the mould itself may be contained to a small area, the spores can easily spread throughout the dwelling.

Mould in buildings

Mould can grow in our homes and workplaces if the above conditions are present. Moisture can be caused by many different factors such as leaking roof or walls, condensation, leaky pipes, rising damp or water ingress due to flooding.

Leaky house syndrome

One very common cause of mould in New Zealand, especially in winter is so-called leaky home, leaky house or leaky building syndrome. This is where timber-framed homes were not built to be properly water tight, especially between 1988 and 2004. The damage bill for this problem alone is estimated at $11.4 billion.

Is mould harmful to health?

Mould itself is not known to cause health problems but for many people, the airborne spores can cause significant problems. Health effects of mould exposure include a runny or blocked nose, irritation of the eyes and skin and sometimes wheezing. For people with asthma, inhaling mould spores may cause an asthma attack. Very rarely, people may develop a severe mould infection, usually in the lungs.

Who is at gr​eater risk of health problems from contact with mould?

People with asthma, allergies, or other breathing conditions are more likely to react to mould. People with weakened immune systems (such as people with HIV infection, cancer patients taking chemotherapy or people who have received an organ transplant) and with chronic lung diseases (such as Chronic Obstructive Pulmonary Disease (COPD) and emphysema) are more at risk of mould infection particularly in their lungs.

Can mould damage your home?

Mould gains its nutrients from whatever material it inhabits. If that is the timber or plasterboard in your house, it can cause both cosmetic and structural damage, including to areas that are not immediately visible. Don’t let mould eat up your house!

How to find mould in your home

Often, the first sign of mould will be a musty odour. If you can smell it, then the mould infestation is already significant enough to cause potential health problems. Other signs to look out for are black spots or other unusual growth, especially in rooms where moisture is present.

How to get rid of mould for good

Eliminating mould can be an easy job or else a complex and demanding one, depending on the circumstances. When handling mould, it is important to take simple safety precautions including wearing personal protection equipment such as a mask and gloves. It is not only important to remove the mould and kill the remaining spores. Unless you modify the conditions that caused the mould in the first place, there is a high likelihood that it will reappear. That’s why we put together this handy nine step guide to help you eliminate mould once and for all.

Nine Easy Steps to Eliminate Mould

Mould is a persistent and unwanted problem in thousands of homes across Australia and New Zealand. Mould can damage the structure of the building and cause health problems for some. See here for more information about why it is essential to minimise mould in the home or workplace.

In this protocol, we recommend the use of an air ozone generator in combination with other natural antifungal agents, as well as physical measures.

Please Note! Ozone can be harmful to breathe. Always follow correct safety procedures when using an ozone generator.


Here are the things you need to follow this procedure*: 

  1. Safety equipment including gloves, goggles and an N95 respirator
  2. Vinegar, buckets, plenty of cleaning cloths
  3. 100ml of tea tree oil
  4. Air ozone generator (5 or 10 gram/hour)
  5. Step ladder if you need to access areas above head height

*Not including measures to eliminate the source of moisture, which will vary according to local conditions.

Step One – identify and remediate the source of moisture.

The steps listed below will help you to remove the mould and spores, but unless the underlying causes are addressed, the problem will likely recur. Mould needs a source of moisture to grow, so it’s very important to find the source of the water that is keeping it alive and take steps to ensure that the dampness problem is managed. You may need to consult a builder.

Case study - our home in Corsair Bay, New Zealand.
The house began life as a beach-side shack and grew over the years to become a cosy cottage. However, the bathroom is on the south side of the house and we were getting black spots of mould on the ceiling.
On the advice of a local roofing expert, we replaced the ageing tin roof. We purchased a dehumidifier and paid attention to the ventilation. The dampness was better, but you could still see the mould on the ceiling. Not all dampness problems are easily solved and you may have to consult a builder or other registered tradesperson.

Step Two – Air Ozone Shock Treatment 

An air ozone generator is a small electrical appliance which uses the available oxygen in the air to create an abundance of ozone gas (O3). Ozone gas has been shown in many studies such as this study The Practical Application of Ozone Gas as an Antifungal (Anti-mold) Agent to have strong fungicidal properties, as well as the documented anti-microbial effects on bacteria and viruses, including SARS-CoV-2.

Warning! Ozone gas is a lung irritant. You must never operate an air ozone generator with people or animals in the room. Please follow all the relevant safety precautions to ensure that this treatment is done safely.  This short video gives a demonstration.      



Ozone is a very reactive gas with a half-life of around 20 minutes at room temperature. So, unlike other chemical agents, there is no toxic residue once the ozone has naturally dissipated. For our bathroom, which you see featured in the video, I used a 5g machine for half an hour. So I set the timer for half an hour, seal up the room, and then don’t go back in for at least an hour, better two. Then you open up the windows and doors, allowing any residual ozone to escape.

The ozone shock treatment will not immediately eliminate all mould, but the evidence suggests it will certainly minimise the dangerous airborne spores, decreasing the risk of accidentally breathing them in while treating the mould.

Treating mould with an air ozone generator will not make the growth disappear. It still needs to be wiped away.

Our bathroom is about 25 cubic metres. I know from my own measurements that 30 minutes with a Purimax-5 will bring the room above 25ppm. What size ozone generator to use depends on the size of the room. Click here for more information on which ozone generator is most suitable for the space you need to clean.

Step three - Examine the extent of the mould.

Safety first. Mould spores are likely to be present, which can be harmful to breathe in. Use personal protection equipment as required. A minimum would be gloves, goggles and an N95 respirator.

Mould can often be identified by the musty odour or else visible growth. Make a thorough examination of the areas where the mould occurs to ensure that you have found it all. Mould loves dark, humid places.

In our case, I could see that mould was growing between the ceiling and a piece of trim. So, I removed that section for the duration of the treatment. 

Step Four – spray and wipe

There are plenty of different agents on the market for treating mould, from the highly toxic to the natural. I am sure they all have their benefits. According to this study, both vinegar and tea tree oil are known to be toxic to many household fungi.

  1. Mix a spray bottle with one part white vinegar to four parts water.

  2. Spray all the affected areas then leave for ten minutes

  3. Wipe off the mould using a fresh, damp rag for each section, ensuring that you do not cross-contaminate. Usually, it will be quite easy to get most of it off, but you may still see a faint outline.

  4. Wipe affected areas with tea tree oil using a fresh rag

There were some areas of our ceiling which still retained black stains after wiping down. A lick of paint cleared that up in no time!

Step Five – Ensure that the area dries out.

Now you have addressed the source of the dampness and treated the mould with ozone, vinegar and tea tree oil. Before continuing with any work such as painting, wait for at least a week to ensure that the dampness has completely gone.

I had taken off a piece of trim because there was mould growing behind. Each step that I applied to the mould on the ceiling, I also applied to the piece of wooden trim. I left it off for two weeks until I was sure that the wall was completely dry.

Step Six – Replace and redecorate

mould resistant paint

Once you are certain that the area has dried out, it is safe to replace any carpentry that has been removed. In some cases, depending on the surface and the type of mould, it may be very difficult to scrub off every trace of the discolouration such as black mould. In this case, we recommend you repaint the area with mould-resistant paint.

Step Seven -Ozone Shock Treatment 2

Once you have completed all cleaning and repairs, it is beneficial to conduct a second ozone shock treatment as described in Step Two. This will help minimise any residual spores and chemicals such as given off by paint and new building materials.

I quite like the smell of paint, but I doubt it’s good for me! Once we had replaced the trim and repainted the ceiling, the bathroom had a strong plasticky smell. One session of ozone shock treatment and that was gone. 

Step Eight – Ventilation is key

Mould requires still air to grow, so to preserve a mould-free environment, ensure that the room has good airflow at least part of the day. Get into the routine of ensuring that condensation does not build up.

Our bathroom has a fan, a heater and a dehumidifier but most of the dampness can be managed by opening and closing the windows according to the time of day.

Step Nine – Maintenance


 Once you have eliminated the mould and removed the source of moisture, the problem may never recur. However, it is wise to keep checking for signs of mould regularly and treat with any of the methods described here before it gets out of control.

So far so good for our bathroom, about six months after we completed the work. We run the ozone generator once a month which keeps it smelling fresh and no mould yet! 


We hope you find this guide interesting and informative. If you require any further information such as which air ozone generator choose for your room, just send us a message, or give us a call.


Simon Thomas

Technical Director

Natural Ozone