Diffusers and Mould

Diffusers and Mould

Many of the homes I assess have essential oil diffusers.

Whilst I love that more people are using essential oils, I have concerns about the essential oil diffusers that harbour mould… and then potentially spread it throughout your home.

So, let me share with you ways to avoid mould – and fragrant oils!

Some key points about essential oil diffusers that require water:

  • they add moisture to your indoor air
  • the water inside them is infrequently changed
  • the tubes within them are impossible to dry out – and this is where I see the most mould – and they are equally impossible to clean!


  • use an electric oil diffuser – such as this one that requires no water at all
  • put essential oils on a cotton ball or tissue
  • grow fresh herbs and enjoy their aroma

Why we Don’t Want to Add Moisture to the Indoor Air

Mould spores are everywhere. They are an important part of our world. We just don’t want them growing in our homes.

Mould requires food and moisture to flourish. Usually the spores are sitting on food. So the thing that we CAN control is moisture.

When there is enough moisture (high humidity levels or a material is wet for 48+ hours) mould can proliferate. This sets off a chain of events, which for those who are sensitive or sensitised can be extremely problematic. Mould can be detrimental to our health as well as to the structure of the building.

Taking steps to reduce moisture levels is ideal – and avoiding adding it is even better!

Want to talk about this? Book a Hidden Hazards Hotline call.

Mould Dead and Alive

Mould Dead and Alive

Mould dead or alive can be a problem.

There are many ways to kill mould, but this does not make it safe for your health.

Dead mould is called “unviable” and alive mould is called “viable.”

Mould is everywhere, however only about 25% of the spores are viable. The rest aren’t, which means they are dead.

In terms of health, mould, viable or not, is a problem.

Parts of mould break off, these are called hyphae.

There are spores released to start new colonies. Some contain mycotoxins and others contain microbial volatile organic compounds (mVOCs).

Some moulds are particularly irritating, allergenic or problematic for health.

Yet for people who are sensitive or sensitised to mould, ANY mould can be a problem.

Here’s a video that I did… Mould Unwanted: Dead or Alive

Please excuse the start where the writing is mirrored – I hadn’t realised it would do that. 🙂


In my years, I have assessed a lot of places (hundreds of them). In many I have found mould, dead and alive.

Mould is often not visible – and can also be hidden.

Remember, mould doesn’t have to be alive to be an issue.

The first part of a water damage and mould Indoor Environmental Health Assessment is the visual inspection. My eyes are trained, and I can easily spot potential issues.

If you would like to have an assessment, please go ahead and book your virtual Indoor Environmental Health Assessment with me – I would be happy to assist you.


If anything becomes wet, it needs to be dried within 48 hours.

This includes a spill on a rug, a burst pipe or even the laundry.

There are many ways that we can create enough moisture to support the growth of mould. As such, you need to be mindful.

You can read more about that here.

Health Practitioner’s Role in Mould and Health

Role of the Health Practitioner in Mould and Health

With the growing awareness of the impact that mould has on our health, there is quite a lot of activity in many areas of the community. As someone who works in this field, it is exciting to see the burgeoning interest of the health practitioner (medical through to alternative health) and that they are getting on board to support people in reclaiming their health. However, it is also somewhat frustrating.


Because health practitioners are knowledgeable in their modality of understanding the health of the body and what to do to support it.

Where it gets frustrating is when health practitioners try to operate outside their scope and claim some mastery of understanding mould and the building, and then what to do.

As both a health practitioner AND a building biologist, I straddle both camps and deeply understand and appreciate the different perspectives.

The Problem is This…

Usually someone who is sensitive or sensitised to mould has done the rounds of health practitioners (medical to alternative) and has spent a good sum of money on tests. Many of these people are struggling to retain an income due to the health issues they face.

When health practitioners recommend testing that does not further the rectification of the issue, what happens is that more money is spent and often a wrong conclusion is achieved.

ERMI – its Role and its Limitations

ERMI (environmental relative mouldiness index) is a test that was developed as a quantitative indicator in settled residential dust of the presence and predominance of mould species associated with indoor fungal growth on building materials. The test was developed to use in scientific research, has been successfully used for this purpose, but is not optimised or recommended for use in individual houses.

The test provides a number associated with the “mouldiness” of a building, ranging from -10 to +20, permitting comparison with a database of 1,083 randomly selected US homes.  Of the tested US homes, 25% exhibited an ERMI score of -4 or less, and 25% exhibited a score of +5 or more.  A home measuring 0 on the ERMI scale would fall in the middle at the 50th percentile “mouldiness,” with half of all homes tested having values below that number and the other half having values above.  A 90th percentile home would therefore be considered very mouldy compared with the average home, and a 10th percentile home, minimally mouldy.


ERMI is Limited

The ERMI metric looks at 26 species of mould more common in water damaged homes. As well, 10 species of mould commonly found in US buildings without water damage are also included. 

The use of the ERMI metric has been validated in the US and several other countries, but not in Australia. This is important due the difference in building materials and design, construction techniques, climate and so forth. All of these factors can all influence the ERMI results.

People have an expectation that an ERMI test will be similar to a pregnancy test. That there’s a 99% likelihood of telling you are pregnant when you really are. And a 99% likelihood of telling you that you aren’t pregnant when you really aren’t. In other words, that there will be very few false positives and very few false negatives. In Australia, we do not have any data with which to judge how accurate these results are. Many homes that are tested may be returning false negatives and false positives.

The ERMI test was originally done by vacuuming a large surface area of dust composited from the bedroom and living room floors, but now the methodology relies on the use of a swiffer cloth. This approach hasn’t been validated.

Further, laypeople collecting samples themselves tend not to use the standardised methodology either, and can introduce positive and negative biases in the readings as a result, increasing false positives and false negatives.

Other types of mould samples (surface and air) identify hyphae and spores, fruiting bodies, and so forth. These potentially provides clues about nearby fungal growth. ERMI is looking at the total mass of genetic components. These details are absent, and therefore the clues are missed.

A Large Standard Deviation = Reduced Useful Information

The ERMI metric has a +/- 3 factor (standard deviation) as described by Vesper (2009). So given a final result of 3, the result is really somewhere between 0-6.

Mould is the most visible part of excess indoor dampness. There is a myriad of other components in the microbial stew initiated by excess indoor dampness. These include increased exposures to multiple allergens such as dust mites, cockroaches, and rodents. The results from ERMI only look at mould.


ERMI doesn’t provide information that helps to pinpoint the cause or location of the moisture problem.

The ERMI test doesn’t help with full identification and development of a remediation plan. A skilled assessor (Indoor Environmental Health Consultant or occupational hygienist) needs to step in and:

  1. Conduct a thorough assessment to locate the problem and the cause
  2. Address the cause – a mould issue is a moisture issue, after all
  3. Do another set of testing that is accurate and useful

So, What Should a Health Practitioner Do?

First and foremost – recognising that there may be a problem with mould and referring onto the appropriate professionals.

What Else?

There are loads of ways that a health practitioner can support their client/patient.

I have offered a lot of really useful and practical ways that you can help your clients/patients in this webinar.

You can watch it right here.

  • Understand mould and the important role it plays in our environment;
  • Become familiar with water damaged buildings and how they can impact health;
  • Become clear on your role as a health practitioner;
  • Introduction to a tool to assist in supporting clients to achieve greater wellbeing.


Tang, W (2007) Petition to EPA

US EPA Office of Inspector General (2013) “Public May be Making Indoor Mold Cleanup Decisions Based on EPA Tool Developed Only for Research Applications” in Report No. 13-P-0356 (22 August 2013): 1-13

Vesper, S (Feb 2009) “Understanding ERMI: How to Get the Most Value from the ERMI Scale” The Synergist (February, 2009): 40-43

Vesper, S, McKinstry, C, Haugland, RA, Iossifova, Y, Lemasters, G, Levin, L, Khurana Hershey, GK, Villareal, M, Bernstein, DI, Lockey, J & Reponen, T (Jan 2007) “Relative Moldiness Index as Predictor of Childhood Respiratory Illness” J Expo Sco Environ Epidemiol. (January 2007); 17(1): 88-94

#mouldhealth #ERMI #betterthanERMI #healthpractitioner