When it comes to indoor air quality, air purifiers are a must. These handy devices were created to help remove pollutants and odors from a house’s air. They will leave your home smelling fresh, reduce dust, and eliminate many allergens that trigger debilitating respiratory issues. So, if an air purifier does all of these beneficial things, why are you smelling a sour odor coming from it? There is actually a very good reason why this is happening, and fortunately, the solution is simple.

The Reason for That Sour Odor

To understand where that sour odor is coming from, you need to know the components of your air purifier. Home air purifiers use a multi-layer filtration system to remove unwanted particles from the air. Most of them will have a HEPA filter or something similar in design, but many also include an activated carbon filter. HEPA filters remove particles, while carbon filters help control odors. Carbon filters are a welcome feature for those who wish to eliminate unpleasant odors from cooking, pets, and other daily activities.

Air purifiers are portable devices that combine filters with a fan. The fan pulls the air in, and unwanted particles become trapped in the filters. Next, purified air is circulated back into your home. This filtration process will repeat many times each hour, continuously contributing to improved interior air quality.

If a sour smell emits from your air purifier, we can usually blame it on the filters. These strange odors are often noticeable after you have used your air purifier continuously for an extended period, but do not worry. Your air purifier is not malfunctioning, and it probably does not need any costly repairs. Those foul odors are proof that the device is doing its job. Simply changing or cleaning the filters will solve the smell.

Which Filter Is at Fault?

After understanding how your air purifier operates, you might assume the HEPA filter is to blame for these awful, sour odors circulating through your home. After all, how can a filter designed to remove nasty odors cause your house to smell worse? Well, the carbon filter truly is at fault. If you take your HEPA filter out and smell it, you probably will not notice any terribly offensive odors. If anything, it may have a dusty or musty odor to it. If you remove the activated carbon filter, however, you might discover a distinct sour smell.

How is this happening? An understanding of some basic science will help explain this phenomenon. Your carbon filter has been working extremely hard to remove all the smelly particles from the air in your residence. After six months of doing this 24 hours a day, seven days a week, it will become too dirty to work effectively. At this point, it will begin to produce a sour smell. This odor is not something to be too concerned about, but you will want to change the filter as soon as possible to eliminate it.

If you want something to blame the sour odor on, look at the construction of the activated carbon filter. There is a high concentration of acetic acid on the surface of the filter. Acetic acid has a distinct sour odor. Your carbon filter also contains a low concentration of propionic acid, but this substance does not produce foul odors.

How the Sour Odor Is Produced

The surface of your carbon filter consists of several chemical elements with oxygen, including carboxyl and lactone groups. When humidity is high, these groups detach from your carbon filter and form acetic acid. In addition, when your carbon filter is near the end of its lifespan, the absorbed chemicals will undergo a reaction in humid conditions. When these things happen, the sour odor you are noticing is produced.

The surface of an activated carbon filter is a carbon cloth. As it does its job, it traps several volatile organic compounds (VOCs) in the air. This layer also catches PM2.5 particles and moisture. All of these factors combine to create the perfect conditions to produce offensive odors.

How to Prevent Sour Odors

If your air purifier uses an activated carbon filter, you will eventually have that sour odor unless you replace it according to the manufacturer’s recommendations. Changing the air filter will also help your air purifier have adequate airflow and operate more efficiently. Otherwise, harmful chemicals, allergens, and dust will be trapped inside of your home. A buildup of unwanted particles in the filters only adds to the disgusting odors you will begin to notice.

If you use your air purifier continuously, have a professional replace your carbon filter every three to four months. You should also wash your filter monthly to keep the surface clean. Having all of your filters changed periodically will help your air purifier maintain good airflow and prevent humid conditions that produce foul odors.

In simpler terms, that sour smell is saying it is time to change your air purifier filters as soon as possible. They have either accumulated too many smelly particles and gas molecules, or they are too clogged to allow for proper airflow.

Other Common Odors

In addition to a sour smell, there are a few other common odors associated with air purifiers that you should understand. For example, you may notice a plastic or sweet smell when you first turn on a new air purifier. The sweet smell also comes from the carbon filter, but this time it means everything is working properly. The plastic smell is due to the manufacturing process of the purifier. The molding procedure used to produce an air purifier gives off strong fumes, and these fumes become trapped within the air purifier. They will release within a few minutes of turning on your unit for the first time. Luckily, this odor is not harmful and quickly dissipates.

You may notice a large combination of foul odors if the air purifier is not getting the ventilation it needs. If you place your purifier in a poorly ventilated area, the filters can become saturated with odor particles. This creates a hub of icky odors that you will notice every time the air purifier cycles on. You can fix this by moving the device to a better well-ventilated location.

Your Air Quality Experts

Bel-Aire Heating & Cooling has been serving residential and commercial clients in Grand Rapids and the surrounding areas since 1961. We can help you with all of your air quality needs, including indoor air quality testing or cleaning and changing your air purifier filters. In addition, we offer a full range of HVAC services, such as system installation, repairs, and routine maintenance. We can also help you find the perfect mini-split for your home, and we offer boiler services, too. By putting our customers first and backing up our work with a satisfaction guarantee, we have earned multiple five-star ratings from our valued clients. Call Bel-Aire Heating & Cooling in Grand Rapids today to schedule an appointment to discuss your home’s air quality!

company icon