Five ways to remove odours from your HVAC system

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Five ways to remove odours from your HVAC system
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Five ways to remove odours from your HVAC system


Unpleasant smells in rooms or spaces where you least expect them? Bad odours have different causes that each require their own way to eliminate. Having evolved before other senses, our smell is a powerful instrument of perception. So, take a deep breath and discover the world of odours and what to do with unwanted smells.

Smell. It’s the first sense you use when born and by the time you become an adult you can distinguish between some 10,000 different odours. Unlike with other senses such as hearing and sight, the smell neurons directly trigger different parts of your brain. Inside the nasal cavity is a part that catches odour molecules and fires a signal to your brain via receptor cells.

Walking into a bakery, freshly cut grass or rain after a dry period. All the associated smells are received through tiny molecules that enter our nose. In fact, all smells are vapours that originate from the source. It is not possible to smell something solid or liquid – what your nose detects is the evaporated liquid.

And that counts equally for grease, diesel, cooking odours and sweat. Here are five ways to ensure these unwanted aromas do not end up in places where they don’t belong.

1) Cleaning filters

Let’s start with an easy one. Inside the air handling unit are one or more cleaning filters sections that sieve out dust and other particles. When all those particles accumulate, they can become a breeding ground for microorganisms, giving off a bad smell and potentially leading to health issues.

Most air handling units are equipped with a differential pressure sensor that gives an alarm when a build-up has occurred. But by then you are actually too late and regular cleaning is the best proactive solution.

2) Balance heat recovery pressure

This tip is especially for systems with a heat recovery wheel inside an air handling unit. These wheels have an efficiency of 70% and are a major asset when it comes to energy savings. They are located on the intersection of two air streams, taking energy from the outgoing stream and transferring it to the incoming.

However, if the balance inside the air handling unit is not properly adjusted, air can leak from the outgoing into the ingoing stream. This can cause bad smells and also lead to a loss of energy efficiency. Check out this blog on how to properly balance the air streams of a heat recovery wheel.

3) Over and under pressure balance

An important point when commissioning an HVAC system is the direction in which air flows and the pressure distribution in a given space. By adjusting the pressure balance in a certain way a negative pressure is created in, for example, toilets, galleys and mess rooms. This can mean that bad odours cannot escape as the negative pressure ensures they automatically stay in the room where they originate and are extracted there.

Over the years, this balance may be disrupted. Repair or changes to the duct system or the installation of a new fan can all lead to an imbalance in the pressure.

4) Active carbon filters

An effective way to neutralise smells is by using an active carbon filter. These are given a special treatment that makes them very porous, allowing them to absorb large amounts of unwanted particles and molecules.

Place the active carbon filter into a stream of air and if the contact time is long enough it will purify the air. Make sure the filter is frequently replaced as active carbon has a certain lifespan. Depending on the situation in which it is used, the filters need to be replaced after a few months. Read more about active carbon filtering here.

5) HVAC scenting

This one is about adding a certain fragrance to the air rather than removing one. HVAC scenting involves diffusing an aroma which disperses throughout the ducting system and into the cabins and rooms. The diffuser system can be connected to an existing air handling unit and the technique is already used in hotels and stores (where it is said to stimulate people to buy specific products).

Final thoughts

Scent is an important factor that contributes to our level of comfort. But that does not mean every smell is necessarily bad. Cooking aromas in a galley or mess hall are not bad. And there is nothing wrong with the smell of diesel in a tender garage or some odours in a toilet. The key issue is when you are confronted with smells in areas where they clearly do not belong.