To deal with viruses an air purifier is needed which is specified to filter out airborne particles in the range of sizes of viruses. There is only one manufacturer in the domestic market that makes an airpurifier that meets this criterium-
The best air purifier for viruses is the iQair HealthPro Plus-the only air purifier that is specified to eliminate 99.5% of particles down to a size of 3nm. Other air purifiers only give specifications for particle removal down to 100nm. Viruses can be as small as 20nm.
For instance Covid-19 was as small as 70nm. Other filters especially H13 HEPA may work, but I am not aware of any other manufacturers that specify the function of their filters for particles below 100nm in diameter. Some manufacturers do however specify that their air purifiers filter out some viruses but do not specify that even small viruses are filtered.
Unfortunately, air purifiers are not a guarantee that you will not catch a virus-for instance someone may cough sending the virus into the indoor air. You could then breathe in the virus before the air gets anywhere near the purifier. Of course it is helpful to have a HEPA air purifier to reduce levels of airborne virus in the air as quickly as possible if there is an infected person in the room. This does make airborne transmission less likely.
IQair report that in a study by Airmid Healthgroup in Ireland which has European accreditation. The test used the H1N1 Influenza Virus (80-120nm diameter) in a room of nearly 30m3. On the highest speed setting the iQair HealthPro reduced the airborne viral load from 27960 ng/m3 to below the detectable measure of 0.156 ng/m3-a 99.95% reduction in 10 minutes. BlueAir has also tested all their air purifiers and found a 99.99% removal of H1N1 virus at 60minutes.
There is also evidence from scientific studies that air filtration can reducce the spread of measles in schools.
The US Environmental Protection Agency states “When used properly, air purifiers can help reduce airborne contaminants including viruses in a home or confined space. However, by itself, a portable air cleaner is not enough to protect people from COVID-19. When used along with other best practices recommended by the CDC, operating an air cleaner can be part of a plan to protect yourself and your family.”
The reduction in viral load by air cleaning will take some time from switching the air purifier on or from someone coughing virus into the air. The amount of virus in the air would be expected to decrease very significantly over 30 minutes if the airflow through the purifier is high enough for the room size. As virus particles can be introduced into the air by breathing the level of virus in the air will never approach zero. However the plateau level will be very significantly lower than without an air purifier. During the SARS epidemic air purifiers were felt to be helpful at reducing infection. The reduction in viral load in the air will decrease both the chance of developing an infection and its severity.
Purifying the air reduces the chance and severity of infection through the reduction of viral load inhaled. Also the severity of infection can also be lessened by the air purifier reducing the number of particles of pollution in the air. Air pollution is present to a greater or lesser extent across all developed countries and is linked to many illnesses including severe viral respiratory infections so the more advanced the filter the better.
Viruses are not the only microorganism that air purification with a filter will remove. Other airborne pathogens, such as airborne bacteria and fungal/mold spores will also be removed.
The other aspects of reducing risk of infection mentioned by the EPA are–
- Increase ventilation with outdoor air
- Improving natural ventilation
- Evaporative coolers
- Use HVAC system and consider upgrading filters
The Advantages of the Hyper-HEPA air filter
This is a filter developed and patented by iQair. It is specified to catch 99.5% of particles down to 0.003um, there is no other corporation that has a filter for use in the home with this demanding specification.
A true HEPA filter is are delicate and can be damaged-they need careful manufacturing, packing, and handling. So filters from an unknown manufacturer without adequate quality control could potentially have defects. The virus in the air could pass through these defects.
The other problem with some cheap air purifiers is that the seals in the purifier can leak and allow non-filtered air to pass around the side of the filter rather than go through the filter so that virus is not removed. The HealthPro Plus has a triple seal to make certain that there is no leak of air around the filter.
Each Healthpro Plus is individually tested and certified that is removing 99.97% of particles greater than 0.1um before leaving the factory. So, it means that there are no manufacturing defects which you would not be aware of. This individual machine certification is unusual and I certainly found it reassuring.
What About Other Makes of Medical Air Purifiers
It is possible that other Hepa H13 and Hepa H14 air filters would remove enough of these very small particles to be effective against viruses. However none are specified down to such a small particle diameter as the iQair currently.
These air purifiers not only directly remove the virus from the air but also help by removing other particles which inflame the airways and make them easier for the virus to infect. The importance of the air purifier removing other particles is shown by-
Pollution in the Air Increases the Risk of Developing Respiratory Viral Illnesses
A common measurement of air pollution is PM2.5-2.5 refers to particles smaller than 2.5um in diameter. It is the number of micrograms of fine particulate per cubic meter of air (ug/m3). That is the weight of pollution in a cube of air 1 meter by 1 meter by 1 meter.
A Dutch study examined pollution data from 355 cities. It found that for every 20% rise in air pollution COVID 19 cases increased by 100%. An Italian study found that in highly polluted parts of Italy the death rate from COVID 19 was increased threefold.
During an H1N1 outbreak air purifiers were thought to be helpful in reducing the infection rate.
So, by removing particles other than viruses the airways the immune system should be more able to fight the virus. People breathing the cleaned air should be less likely to develop an infection. Even if a virus is breathed in when outside the home.
Air Pollution Can Increase the Severity and Mortality of Respiratory Viral Illnesses
Researches at the Harvard TH Chan school of public health investigated whether air pollution could increase the severity of COVID-19. They measured the PM2.5 in 3000 US counties and found that the severity and chance of dying from COVID increased with increasing air pollution. The increase was 8% for every 1 ug/m3 increase in average air pollution. So, if the average air pollution in your area were a relatively low 10ug/m3 (still a “safe” level) your risk of dying from COVID would be 70% higher than if the pM2.5 in the air was 1 with an air purifier.
Another study found that exposure to PM 2.5 from wildfires impairs the ability of the immune system to fight viruses. This was by stopping macrophages, which clear debris, from becoming activated. This effect lasts for up to a week after exposure to pollution.
A further study in 2014 found that in children having pollutant particles in the lungs –
- viruses reproduced and spread more quickly in the lungs
- white blood cells lost their ability to deal with the virus
- viral material was cleared more slowly from the lungs
So by removing pollution particles from the air the airways should be in better shape to fight any virus. This will then lead to milder disease. So any HEPA filtration with adequate air flow should help. It would of course be even better to have one specified to remove virus.
A UV Air Purifier is Not the Solution
UV light (Ultraviolet light) can destroy the DNA of micro organisms such as viruses. However this process needs enough energy so the virus would have to be near the UV C light for some time. This is not possible in an air purifier as a large volume of air needs filtration at a rapid rate. This means the virus passes by the UV light too quickly for it all to be inactivated. If the air purifier is run on its slowest setting to allow more time for the UV light to irradiate the virus particles the air filtration rate will be too low to effectively remove them. Commercial air sanitizers are much more effective but need to be wall mounted and continuously irradiate the whole room with UV light. They are not suitable for homes.
An ozone generator is not the answwer because ozone in concentrations high enough to destroy viruses would be damaging to human health. Ozone irritates the airways in the lungs and is responsible for some of the adverse health effects of smog.
A carbon filter removes chemicals such as volatile organic compounds and is not helpful for inactivating or filtering virus particles.
HVAC Filters are Also Not the Solution
HVAC Filters are present in HVAC system to protect the system from particles and keep it running. So they are designed to keep large particles out of the fan and heating and cooling coils. They are in general not able to filter out very small particles. It is possible to modify your system to make an HVAC air filtration system by improving the filtering to better protect you and your family-see this article.
The iQair HyperHEPA filters are specified to filter 99.5% of particles down to 3nm. Other manufacturers do not specify filtration rates at less than 100nm. Viruses vary in size but can be as small as 20nm in diameter. So we have no guarentee from other manufacturer’s that their purifiers will remove viruses. So the best choice of air purifier would seem to be an iQair.
It may be other manufacturers’ filters will work well for particles the size of small viruses. However without data for the performance of their filters at low particle sizes we do not know.