Air purifiers are devices which are designed to remove contaminants and pollutants from the air around you so as to increase the ambient air quality of the space you are in.
They are generally holistic in their ability to combat air pollution. This means that they are intended to remove all types of air contaminants.
These include particulate matter, which is made up of ultrafine particles smaller than 10 microns which can enter your lungs and bloodstream, as well as gaseous pollutants, such as gaseous chemicals (especially acids) or noxious gases such as NO2 and SO2 .
Apart from these two broad categories of pollutants, many air purifiers also remove large dust particles and bad odours, especially those from kitchens and cigarettes.
They also combat allergens such as pollen and animal dander.
As bi0-contaminants especially virus is very small in size, to accomplish removal, purifiers use a variety of technologies.
A common filter is a mechanical filter, usually a HEPA filter, which has extremely small pores which do not allow particulate matter to pass through it.
Very often, this is coupled with an activated carbon filter which adsorbs gases and odors onto it for another level of purification.
More recently, air purifiers have also started combating microorganisms and biological contaminants in the air to prevent users from diseases and infections.
These biological contaminants include bacteria, mould spores, and viruses alongside small insects such as dust mites and insect droppings.
These new air purifiers are discussed more fully in the next section.
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Can Air Purifiers Remove Virus / Bacteria?
Yes, air purifiers today can remove/kill bio-contaminants such as mould, bacteria, and viruses. But the effectiveness varies based on the purification method and is never 100%.
As stated above, biological contaminants include microorganisms such as mould, viruses, and bacteria as well as larger contaminants, most commonly dust mites and droppings from insects such as cockroaches.
Very often, these microorganisms continue to circulate inside your house and even increasing in number, which makes them different from contaminants such as particulate matter or gaseous pollutants which cannot increase their own concentrations.
Thus, if they are not removed from the air in your house, you can have an increased risk of catching various diseases.
While earlier air purifiers were not designed to remove microorganisms from the air, there has been a great increase in the number of purifiers in the market which now also have this functionality.
They use a variety of filters and technologies, some of which are specially developed to remove microorganisms, to treat biological contaminants. This can include either removing them from circulation in your house or sterilizing and killing them.
Many air purifiers now remove bacteria and mould from circulation in your house using mechanical filters such as a HEPA filter which has pores smaller than the size of the bacteria and mould .
Different air purifiers are also designed to focus on different types of disease-causing bacteria and are very often marketed as being especially efficient against particular types of viruses, though they are not 100% effective in doing so.
Air Purification Tech. To Handle Bacteria / Virus
Nowadays air purifiers use a number of technologies to eliminate microorganisms from circulating in your house.
These include new technologies specifically developed for this purpose, such as Ultraviolet Germicidal Irradiation (UVGI) or ionization, or a modification to traditional filters such as modern HEPA filters.
Often, two methods are used together to ensure sterilized air.
This is important that while some technologies can kill the bio-contaminants they cannot remove other air pollutants such as smoke, dust, etc.
The following technologies are currently used in air purifiers to combat microorganisms:
1. HEPA Filters
HEPA filters are traditional mechanical filters with extremely small pore sizes.
These pores can trap particulate matter as small as 0.3 microns in size.
Since many household disease-causing bacteria are between 0.3 microns to 60 microns in size, they are also trapped in the filter and are prevented from circulating in your house.
Newer variants of HEPA filters can even trap microorganisms as small as 0.03 microns .
However, bacteria and mould that is caught in the filter can grow on the filter itself or release toxins into the air, which is often hazardous to health.
To combat this, some modern HEPA filters are also made of fibers with antimicrobial properties which kill off the bacteria and spores stuck to the filter.
The efficiency of HEPA filters is 99.97%, which means that out of 10,000 particles filtered only 3 manage to pass through it.
- Extremely high effectiveness rate (99.97%)
- Filters out particulate matter as well as bacteria, mould, and dust mites
- Cannot kill or filter out viruses
- Bacteria and mould can grow on the filter if it is not made of antimicrobial fibers
2. Ultraviolet Germicidal Irradiation (UVGI)
UVGI technology is used to specifically target microorganisms.
It works by using a UV light which causes damage to the DNA of bacteria, mould, and viruses which is severe enough to either kill them or prevent them from reproducing.
It works by either targeting the air flow through the air purifier itself or by focusing the radiation on another filter which traps microorganisms .
Since this technology is only intended to combat biological contaminants, it is used in conjunction with another filter, such as a HEPA filter.
It can eliminate 99% of microorganisms if it is pointed at a filter which catches microorganisms.
In a residential setting, these types of air purifiers can be less effective since they require a slow flow of air through the air purifier over a long period of time.
Furthermore, since this technology is new for air purifiers, there are still no official guidelines over the dosage of UV light which means that some UVGI air purifiers can also lead to the formation of ozone, which can be dangerous.
- Can be as effective as eliminating 99% of microorganisms
- Can create Ozone as a byproduct which can lead to health issues such as lung inflammation and chest pain
- Maybe less effective in residential settings and need to be paired with another filter
3. Ionizers and Electrostatic Precipitators
These two types of filtration systems are often clubbed together because they both work through imparting an electrical charge to pollutants in order to collect them more effectively.
In electrostatic precipitators, the air that passes through the air purifier goes through two electrically charged plates in which contaminants such as dust but also bacteria and viruses get electrically charged and attracted to an electrical plate.
This filters them out from the air flow in your house.
Ionizers, on the other hand, work by sending charged particles or ions through your house.
These ions stick to contaminants and force them to settle to the ground. More recently, air purifiers use internal ion beams which sterilize and kill any microorganisms which pass through the purifier.
This type of filtration can have an efficiency rate of anywhere between 60% to 95% depending on how clean the electrical plates are as well as the individual models and companies which manufacture them.
A downside of this method is that is can often generate harmful ozone.
- Tackles particulate matter as well, not just microorganisms
- Can be highly effective (up to 95% effectiveness)
- Effectiveness can decrease over time and requires frequent cleaning of electrostatic plates
- Can produce Ozone as a byproduct which is injurious to health
- Charged dust particles have a larger chance of being breathed into the lungs before settling down on the floor
4. Ozone Generators
This is a somewhat controversial method of air purification since it uses an ozone molecule for air purification.
This ozone is generated inside the air purifier by taking in oxygen from the surrounding air and using either high powered UV light or electrical discharge to change oxygen molecules into ozone which then reacts with the contaminants which flow through the purifier.
Ozone is made of 3 oxygen atoms and it readily turns into an oxygen molecule while oxidizing pollutants such as gases, odours, and biological contaminants.
This oxidation causes great damage to bacteria, fungi, and viruses and can very often kill them off.
According to EPA (United States Environmental Protection Agency) –
Available scientific evidence shows that at concentrations that do not exceed public health standards, ozone has little potential to remove indoor air contaminants.
Ozone generators have been shown to have limited effectiveness and hence they are often coupled with ionizer technologies.
While the ionizer affects dust and particulate matter, the ozone generator works on the microorganisms.
- A powerful method of killing off microorganisms
- Limited effectiveness when used on its own
- Ozone can cause multiple health issues from aggravating asthma to lung pain and inflammation of respiratory tissues
5. Thermodynamic Sterilization
This is one of the newest technologies for residential air cleaners and purifiers.
In these types of air purifiers, the air is taken in through micro-capillaries and is then subjected to hot blasts of air to sterilize and kill bacteria, mould, and viruses.
It uses the heat of up to 200C and has a purification rate of 99.9 %.
However, thermodynamic sterilization does not filter air and hence it must always be combined with other filters for use in proper air purifiers.
Because this technology is relatively recent, it does not yet have official standards or guidelines, such as those set by the American EPA, in place.
- High-efficiency rate
- Tackles all microorganisms and biological contaminants
- Does not filter other pollutants
- No official standards have been set for this method yet
New technological innovations in air purifier technology have given purifiers the ability to remove biological contaminants from the air alongside traditionally measured contaminants such as gaseous pollutants and particulate matter.
This is accomplished through modifications to traditional filters such as HEPA filters or threw new and up-and-coming technologies.
These new methods include thermodynamic sterilization and ultraviolet germicidal irradiation (UVGI) and have varying degrees of effectiveness, although most of them are known to be 90% effective.
These technologies give you a wide range of choices to choose from in the market, although in India so far HEPA filters, ionizers, and electrostatic precipitators are the most common filtration methods.
Many purifiers mix and match various methods to give you the optimum protection from microorganisms and the infections that they can cause.