HEPA filters (High-Efficiency Particulate Arrestance) do not remove odors. Bad smell is caused by extremely small particles that cannot be removed by HEPA filters. To remove odor, you will need other filters, such as an activated carbon filter. Some air purifiers come with both a HEPA filter and a filter to remove odors.
Removal of odor does not happen via filters such as HEPA. Later in this article, you can read exactly why HEPA filters are not fit for odor removal. But first, let’s have a look at what does remove odors.
What type of filter removes odors?
The most common odor filter is an activated carbon filter, also called a HEGA filter (High-Efficiency Gas Adsorption). An activated carbon filter is specifically designed to remove odors.
Filters such as HEPA work somewhat like a net and trap particles that hit the fibers as the air passes through the filter. However, odor particles are so small that another technique is required. A technique at which an activated carbon filter excels. This technique is to make the odor particles stick to a surface and thereby removing them from the air.
Activated carbon filters
Activated carbon filters are made from carbon, also known as charcoal. This material is very effective at removing odors, but is also commonly used in cosmetics.
Activated carbon makes molecules stick to their surface. This is called adsorption (the more commonly known absorption, written with a b instead of a d, works similar to a sponge). Adsorption (with a d), makes particles stick to their surface. Therefore, the larger the surface area, the more particles can be adsorbed.
Activated carbon is ‘activated’ with a form of treatment that increases the surface area of the carbon. A larger surface area means that more molecules can be removed. One gram of activated carbon has a surface area of about 3,000 m2 (32,000 sq ft). Because of this, an activated carbon filter can take up a lot of tiny smelly molecules.
Odor particles are too small for HEPA filter
HEPA filters are filters that remove tiny particles from the air. However, particles that cause scents and odors are extremely small (a few nanometers at most: 0.000001 millimeters) and cannot be removed by a HEPA filter. Even though HEPA filters are the current high-standard particle removal filters, odor particles are much too small.
Even though a HEPA filter is great at removing particles as tiny as 0.01 micrometers (0.0001 millimeters), it cannot remove odors. Odor particles are at most a few nanometers in size (0.000001 millimeters), which makes me even more impressed with the ability of our nose to detect smell!
HEPA is still essential for good air quality
Although HEPA filters do not remove bad smell, they are an essential part of a good air purifier. HEPA filters remove many tiny particles from the air and are, as the name suggests, highly efficient in doing so. HEPA filters remove fine dust, pet dander, pollen, and dust mites. In total, HEPA removes about 99% of airborne particles.
Can I have both odor removal and HEPA?
Yes, you can! Many air purifiers come with a variety of filters including a pre-filter, a HEPA filter, and an activated carbon filter.
Often, a HEPA filter is preceded by a pre-filter that removes larger particles. In this way, the HEPA filter will not get clogged with large particles and can do its job removing the tiny ones. In addition, an odor filter such as activated carbon can be included.
The best air purifiers that include HEPA and odor removal
Comparing quality and price, the best air purifier that includes both a HEPA filter and an activated carbon filter currently is the Coway Mighty. The Coway Mighty is a small and affordable air purifier that is capable of maintaining clean air in rooms of up to 361 square feet (33.5 square meters).
The following table shows my selection of the best air purifiers that both remove odors and contain a HEPA filter. The table below shows four great air purifiers and their specifications.
| Air purifier | Why this purifier? | Room size | Cost (approximately) | Activated carbon or Zeolite | Ionizer | ACH | Extra |
|---|---|---|---|---|---|---|---|
| GermGuardian AC4825E | Contains HEPA filter, high rated (amazon), cheap purifier | 167 sq. Feet (15.5) | 83 dollars | Activated carbon | No | 4 | UV-light germ and mold killer |
| Coway mighty | Contains HEPA filter, one of the most popular air purifiers available | 361 sq. Feet (33.5 m2) | 250 dollars | Activated carbon | Yes, but can be turned off | Has fan speed options | Air Quality Indicator, Auto Mode, Eco Mode |
| Levoit Core 300 | Amazon best seller HEPA filter #1 | 219 sq. Feet (20 m2) | 100 dollars | Activated carbon | No | 5 + has fan speed options | Filter replacement indicator, |
| Coway Airmega 400 Smart | Contains HEPA filter, smart purifier with many features and large area coverage | 1.560 sq. Feet (145 m2) | 640 dollars | Activated carbon | No | 2 for 1560 sq. feet, 4 for 780 sq. feet | Shows air quality in a phone app. Adjusts speed based on measured air quality. Filter replacement indicator, |
