why does my air purifier smell sour

Sometimes we find the air purifier smells bad sour or funny when we are using an air purifier. So Why does the air purifier have a bad smell after using it for a period of time? This has a great impact on our use. Here is an analysis of the reason and a solution of air purifier stinks for everyone.

Sour and Dusty Smell from the Column Activated Carbon Filter

The filter used in air purifiers is generally composed of HEPA filter and activated carbon filter. Some air purifiers are composed of an integrated filter. The activated carbon of the filter is divided into columnar activated carbon. The columnar activated carbon filter is generally an independent filter layer, which is composed of two large filters, a HEPA filter and an activated carbon filter, and the filter composed of an integrated filter is called a carbon cloth. Through the test, the HEPA filter basically does not produce sour smell, and some only smell of dust. The columnar activated carbon filter layer emits a slight sour smell after 3-4 months of use (24 hours of long-term use), which is actually quite normal.

air purifier smells bad

Sour Smell from the Integrated Filter

The integrated filter screen is composed of a filter screen (with carbon cloth). The simple understanding is that activated carbon is added to the ultra HEPA room air purifier. The activated carbon has a large surface area and strong adsorption capacity. It can also filter dust and particulate pollutants. It is the main reason for the bad sour smell of air purifier stinks.

Through testing, the most sour suspect: acetic acid—its concentration has a very high positive correlation with "sour taste" (propionic acid has a high correlation, but its concentration is very low). The surface of activated carbon is rich in a variety of oxygen-containing functional groups, such as carboxyl groups, lactone groups, etc. These oxygen-containing functional groups are easy to fall off to form acetic acid in a humid oxygen environment.

why does my air purifier smell
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When the activated carbon is close to saturation, there will be a large amount of adsorbed formaldehyde, toluene and other volatile organic compounds on the surface of the activated carbon. A large amount of these volatile organic compounds will produce complex chemical reactions under wet oxygen conditions. After the reaction, there will be acetic acid. There are PM2.5 particles with the same huge surface area and extremely active chemical properties on the surface of activated carbon, so the rate of acetic acid production will increase.

Through the above explanation, everyone knows why the integrated filter-carbon cloth is more prone to produce sour smell, because the granular carbon in the carbon cloth has a larger surface area. A large surface area means more oxygen-containing functional groups, and carbon is inserted. The surface of the cloth has a large amount of volatile organic compounds, PM2.5, and water. Under such an environment, it is the best place for chemical reactions, and the rate of acetic acid production is very fast.

How to Choose an Air Purifier Without Smell?

The above explanation has been very clear, the main reason for the air purifier stinks or smells bad sour is the structure of the filter, especially the kind of carbon cloth filter.

Therefore, when choosing an air purifier, we try to avoid choosing the kind of air purifier that uses the activated carbon filter inside, especially the kind of carbon cloth filter. Try to avoid choosing an air purifier with an integrated filter. Choose those air purifiers that use columnar carbon for the internal filter, and try to choose the air purifier with a multi-layer filter structure. The activated carbon filter and the particulate filter can be separated to reduce the generation of bad sour funny smell.