Sat 1 Jun 2024

Healthy air, healthy life: Identify and avoid mold in your air conditioner

The importance of indoor air quality has been growing since the pandemic. ​​According to our Big Ideas Survey - Customer Lens, 57% of respondents are more worried now than they were before COVID about the quality of the air we breathe and how it affects our everyday life and health.
While several invisible factors can influence air quality, some, like Mold, show noticeable signs that require special attention.

Air Conditioner mold: Conditions that promote growth

mold loves warm, moist, and dark places that are between 25°C to 30°C and relative humidity levels exceeding 65%. These specific characteristics provide an ideal environment for mold to grow, and unfortunately, your AC can become the perfect setting for this if it is not properly maintained. 

It only needs an organic food source – like dust – and it’s ready to grow. 
We all know how bad mold looks, and most importantly that it is not good for us. Mold produces allergens, irritants, and in some instances, toxic substances. Touching or inhaling mold or mold spores can have different reactions – especially for allergic people. You can experience allergic reactions such as sneezing, a runny nose, red eyes, or skin rash – typically associated with Hay fever and it may pose a risk to asthma sufferers. 

 Woman sneexzing at home because of poor indoor air quality

Identifying mold in your AC:

Fortunately, detecting the presence of mold in your AC is quite simple.

If there is a musty smell or ammonia odor circulating in your home or when your AC is on, this is your first sign that there might be mold in your unit. We have interviewed over 2,700 air conditioner owners from all over the world and found that more than half of consumers had experienced bad smells coming out of their air conditioning indoor units, this concern is a big pain point because there’s a belief that smells affect health. 43% of our respondents agree that bad odors affect how they feel about the air quality in their homes.

In case you do detect this particular odor, but you haven’t actually seen evidence of mold in the HVAC system, you should open your AC unit to check for mildew. You should look for fuzzy patches in green-black colors – even though mold can be brown, pink, white, yellow, or orange, usually green/black is most common.

How to prevent mold in ACs and what to do when you detect it

According to our survey: two-thirds of the respondents find it hard to remember when to clean the filter, as well as hard to clean it. Most people don't know what, how, or when to clean their AC unit, and removing mold can be difficult, and unpleasant and it must be done carefully. If your AC has mold, we advise you to call a professional to have it safely removed.

At Hitachi, multiple features and technologies have been developed and are designed to keep your indoor unit’s interior clean over the years and to look after the health of your AC and, thus, yours too.

mold Guard is the tech that will help you address this concern – a solution specifically designed to simplify the process, reduce mold formation, and eliminate unpleasant odors in air conditioning. Let's explore how this technology works:

mold Guard 2.0 constantly monitors the temperature & humidity level through sensors inside the indoor unit, even when the indoor unit is turned off. When sensors detect a combination of factors favorable for mold growth inside the AC unit continuously, for a specific amount of time (168 hrs) ①, mold Guard will activate ②. The coil will heat and dry the inside to reach the ideal conditions (30% RH and 40°C - 45°C) to kill mold within 10 minutes.


So, next time you have your AC off for a long period, you can rely on mold Guard to regularly check it and prevent mold growth.

mold guard function (for heat pump AC) *

Whenever the unit is switched off, the mold guard function automatically blows air through internal components and heats the coil up to 50˚(1)C to prevent the build-up of mold – the primary cause of those nasty odors

(1) The temperature of coil heating may differ depending on ambient and indoor conditions.


mold guard function (for cooling-only AC) *

Whenever the unit is switched off, the mold guard function automatically blows air through internal components to prevent the build-up of mold – the primary cause of those nasty odors.

*The mold guard function can prevent mold growth inside the indoor unit but not remove existing mold.


But what if the mold grows in the heat exchanger? There’s a solution for that too! Just visit the Frostwash page and learn all about it!

Johnsons Controls-Hitachi Air Conditioning is committed to developing solutions to preserve your indoor air quality, the lifespan of your AC, and your health: Healthy air = healthy life. To learn more about mold Guard, our solutions and other features, visit the web




Johnson Controls-Hitachi Air Conditioning