Is an Air Purifier Necessary

Historically, evidence has been weak that air cleaning devices are effective in reducing asthma symptoms associated with small particles that remain in the air, such as those from some airborne cat dander and dust mite allergens. However, the American Academy of Allergy Asthma & Immunology reference a study done by Jhun et al. in 2016 published in The Journal of Allergy and Clinical Immunology: In Practice.

It was the first study to assess the effectiveness of HEPA filters in school classrooms in the inner-city as it pertains to asthma morbidity. Although the focus was not on health benefits of air purifiers, the evidence was clear that it certainly improves asthma symptoms and lung function. More studies need to be done to fully evaluate their effectiveness and hopefully this study will spark that.

A quote from the article:
“In the intervention group, the authors observed a significant reduction in indoor particulate pollutants—fine particulate matter was reduced by up to 49% and black carbon was reduced by up to 58%. The magnitude of reductions was within the range reported by previous studies to have clinically meaningful effects on asthma morbidity. While the pilot was not powered to evaluate health effects, the authors found modest improvement in asthma symptoms and lung function in the intervention group.”

Besides home indoor air quality, there are a rising number of complaints from people suffering acute health and comfort effects associated to what is termed Sick Building Syndrome (SBS). Often the result of flaws in the HVAC system, or off-gassing from materials, VOCs and others, the need for buildings to have improved air quality is increasing. I’m wanting to get a little air purifier for my office desk. My eyes burn when I’m in the office!

Common Indoor Air Pollutants

It is important to note that air purifiers can only purify air borne particles, and not those that have already fallen to the ground. It is essential to combine your air purification with other indoor cleaning methods.

Volatile Organic Compounds (VOCs)

VOCs are organic chemicals that vaporize at room temperature. They can be harmful to your health in the long run and are becoming increasingly prevalent. We need to be aware of what these chemicals are, what they’re found in and then replace those products with greener ones.

VOCs include specific compounds such as benzene, formaldehyde, perchloroethylene, methylene chloride, tetrachloroethene and others. And can be found in tobacco smokes, exhaust fumes, new carpets, paints, aerosols, dry cleaning, synthetic fibres, refrigerants, ceiling tiles, plastics, glues, adhesive removers and cleaning materials. Personally, I refuse to use the usual cleaning products in my home – both for household cleaning and the laundry.

Short-term exposure effects include irritation of eyes, nose, throat; headaches; nausea / vomiting; aggravation of asthma symptoms; and dizziness. Long term effects can include increased risk of cancer; liver damage, and kidney damage.

Airborne Particles

Most allergy and asthma triggers come from this group of irritants. Airborne particles such as pollen, pet dander, mold spores, fungi, and dust mite feces gas.

Odors and Gases

Fumes from cooking – use a hood, radon, carbon monoxide and other toxins. Lose the hair spray – aerosols are harmful. Get rid of the gloriously scented candles or air fresheners – they are harmful. Opt for natural, green products instead. Try find other ways to get rid of ants or other unwanted critters – pesticides are harmful. Lose the wood burning fire place, and quit smoking

Micro-Organisms

These are the viruses, bacteria, pathogens and antigens that make you sick. Your sick kid sneezing them into the air, the A/C or indoor heating disseminating the germs of your sick spouse throughout the house. Mold is lumped into this grouping, too.

Types of Air Purifiers

Now that we’ve looked at what pollutants may be lurking in your air, let’s find out what types of air purifiers are out there and which removes what contaminants.

There are a number of different types of air purifiers. It really is important to research each type to know what will help your specific need. 

Filter-Based (HEPA, MERV)

These are systems physically trap particles as air is forced through a filter. The size of particle that is filtered is dependant on the type of filter. Here are the two main filter-based air purification systems:

1. HEPA (High Efficiency Particulate Arrestance)

HEPA filters provide the highest air cleaning efficiency, capturing 99.97% of all airborne particles as small as 0.3 microns (symbol: µm), that other filtration systems would re-circulate back into your home. They are your best option if you’re looking at purchasing an air purifier to relieve allergy and asthma symptoms. Be careful to choose only true HEPA filters and not HEPA-type or HEPA-like filters, which do not meet the HEPA standard. HEPA filters are more common in standalone air purifiers and not so much for whole house solutions. In fact, the air purifier that I bought for my bedroom is a pure HEPA and I LOVE it.

Some facts about pure HEPA filters:

 – removes 99.97% of 0.3 µm particles (a requirement of the US Department of Energy)
 – often comes with a pre filter to capture the coarser, bigger particles
 – often works together with an activated carbon-based material to absorb harmful gases or odors
 – they do not produce ozone or emit any harmful emissions

Examples of some common air contaminants and their size in microns:
 – Pollen (5-100 microns)
 – Mold (2-20 microns)
 – Pet Dander (0.5-100 microns)
 – Dust Mite Debris (0.5-50 microns)
 – Bacteria (0.35-10 microns)

HEPA filters are able to remove all of the contaminants above because they are larger than 0.3 micron.

Pros
 – Removes dust, pollen, mold spores, dust mites, and other allergens.
 – Removes most bacteria
 – Solid particles captured are not released into the air again

Cons
 – Does not remove chemical fumes, cigarette smoke, or odors.
 – Not as effective in capturing the smallest viruses
 – Micro-organisms captured in filter can breed or reproduce, resulting in increased micro-organism populations

According to the American Academy of Pediatrics Allergy and Immunology (2003), HEPA air filtration systems are recommended to reduce exposure to indoor asthma triggers.

2. HVAC MERV

These filters are used in HVAC units. The term MERV refers to the minimum efficiency reporting value which rates the effectiveness of the filter. For example, a filter at MERV 14 or above will remove airborne particles 0.3 microns or larger. A high efficiency MERV 14 filter can remove 75% of 0.3 µm particles. The top performing filters typically have a MERV higher than 10.

When looking into whole house air purification, consider a high efficiency MERV 14 filter. You may need to have someone change the the size of your slide-in furnace filter, since these filters are a lot thicker and denser. Also, when installed, it needs to be air tight so that no air bypasses the filter.

Although much less expensive to buy than a powerful HEPA, you may find quite a jump in your energy bill. Since these filters are so much denser, the air being forced through them faces increased air resistance, and needs to be pushed at harder rate.

If you use a Filtrete filter by 3M, you’ll notice another rating system on their products – namely a MPR rating. This stands for Microparticle Performance Rating and was developed by 3M to rate the filter’s ability to capture the smallest airborne particles – from 0.3 to 1 µm in size.

MPR is different from MERV, the Minimum Efficiency Reporting Value. The MERV system measures a filter’s ability to capture large particles. The MPR only takes into account the microscopic particles between 0.3 and 1 µm.

3. ULPA (Ultra Low Penetration Air)

These ultra efficient filters are mostly used in research labs. They can filter our nano-particles, at least 99.999% of dust, pollen, mold, bacteria and other airborne particles with a size of 100µm or larger. In contrast, HEPA can filter out 300µm and larger.

Non Filter-Based

1. Ozone Generators

Let’s just get this out there straight away, don’t buy any ozone generating ‘air purifier’ – ozone is not safe for humans to inhale. Ozone generators emit large amounts of strong ozone gas to oxidise other chemicals. They are only safe to be used in unoccupied rooms, and are used to remove the smell of decaying flesh at crime scenes.

2. Ionizer Purifiers

Ionizer purifiers generate electrically charged air or gas ions. These ions attach to airborne particles which are then attracted to a larger plate. These purifiers don’t filter, rather by attaching to pollutants they make them heavy enough fall to the ground where they are to be vacuumed or cleaned. They either come with a fan or without. The ones with a fan are more effective. Most ionizers produce less than 0.05 ppm of ozone (industrial safety standard). I have a small one in my car.

3. Activated Carbon

Activated carbon adsorbs (not a typo) gases and odors at a molecular level that are too small to be trapped by a HEPA filter. The molecules attach to the carbon, this process is called adsorption. Many HEPA filters also have an activated carbon filter – mine does and it works great. It’s important to note that this only adsorbs some gases and odors, so be sure to know which ones the particular substance adsorbs so that it meets your needs.   

4. UVGI (Ultraviolet Germicidal Irradiation)

Ultraviolet Germicidal Irradiation sterilizes the air as it passes over UV lamps. As the name ‘germicidal’ suggests, they kill germs – viruses, bacteria, pathogens and antigens. I love that about my HEPA purifier, it also has a UV light that I can switch on and off when needed.

5. TSS Thermodynamic Sterilization

TSS is also not a filtering method, instead it incinerates particles with high heat. It claims to not emit harmful emission, no ions, and reduces ozone in the atmosphere. It runs silently and you don’t have to worry about replacing or washing filters. A little pricy, but if it meets your needs, then well worth the investment.

6. Electronic (Electrostatic) Air Cleaners

Electronic, otherwise known as electrostatic, air cleaners function at the same level as true HEPA filters. They’re great in that they have washable filters and often run more quietly. Two drawbacks, however, is that can produce small amounts of ozone (known lung irritant), and many of them require very frequent washing (some even daily) to work effectively.

7. Polarized-Media Electronic

These create a type of electric field where airborne particles become polarized and stick to a disposable media pad. Their effectiveness increases as they load, as each time the air passes, more ultra fine particles (UFPs) are removed. They don’t produce ozone and are highly efficient.

What Really Counts

By now, you’re likely getting a better perspective on what it is you need and what is out there. Before you click on any links to make your purchase, there are some other important factors you need to look out for.

Noise Level

Noise level is measured in decibels dB(A) which isn’t always easy to translate into what you’re comfortable with. If you’re sensitive to noise, be sure to read users’ reviews to see how it’s affected them. A regular air purifier on low sits at about 36 dB(A) and a good air purifier at about 32 dB(A).

If you’re like me, I need white noise to sleep. Before I got my air purifier, I would put the fan on to have white noise. If you like total silence, then a fan-based purifier might not work for you. Another option would be to purchase a more powerful unit that you run at a lower speed more quietly, instead of a smaller unit that you crank up to the max at a louder higher speed. Many air purifier buyers make the mistake of saving money by selecting a less expensive purifier when the most powerful model in that same vendor’s product line is maybe only $20 higher.

Room Size

Make sure that the unit you are purchasing can service the size of the room you’re intending to place it in. Obviously, if you’re aiming for a whole house solution, then this isn’t a concern. Be sure to check this, otherwise you’re air purification won’t be effective.

Portability

If you’re wanting a unit that you can move from room to room, then be sure to check how portable your unit is. The one I have in my bedroom has a handle and is easy to move around. Others are heavy, or even require some form of installation.

ACH Rating

The ACH rating, rates an air purifier on the number of Air Changes per Hour. Naturally, the less air changes, the less effective the device and the longer it takes to purify the air.

CADR

CADR, Clean Air Delivery Rate, measure the cleaning speed of air purification systems. A CADR above 350 is excellent, a CADR below 100 is poor. Multiply the CADR by 1.55 to calculate the optimal number of square feet that unit can handle. For example, an air purifier with a CADR of 100 can effectively clean the air of a room that is 155 square feet. A unit with a lower CADR will also work in a room of that size, but not as efficiently or as effectively.

Emissions

Are there any harmful by-products that the device emits, such as ozone? How much ozone are you ok with? My car air purifier emits a small amount of ozone, but it is way below the safety level and a lesser evil, in my opinion. If the emission was higher, I wouldn’t choose that purifier.

Energy

Are you concerned about energy consumption? Look for an air cleaner that has an Energy Star rating. As mentioned before, if you purchase a more powerful unit, you can run it on a lower level which would be less taxing on your energy bill. Also, you need to keep your filter clean, dirty filters will pull on more power. So far, I haven’t found a huge increase in my bill, but I only use my unit at night. When are you wanting yours to run? At night, all the time, in every season? All of these are factors.

Purchase Cost

Definitely a point that can effect our purchase, but make this decision once you’ve narrowed down a few options. Sometimes it pays off to spend more for markedly better results and less spend in the long run with maintenance. 

Maintenance

How much is it going to cost you to maintain your air cleaning system both in time and money? Washable or vacuum-able filters and pre-filters are a great cost saver but can be a pain in the butt if they need very frequent cleaning. Then again, disposable filters can be costly especially if they need to be replaced fairly often. Check how frequent filters need to be replaced (assuming you’re looking at a HEPA air purifier).

Warranty

Often forgotten, but so important. Check if your purifier comes with a warranty and what the terms and conditions are.

Aesthetics

For some us, aesthetics are an important factor. We don’t want an ugly brown box sitting in our beautifully designed bedroom or living room. We’d rather pay a little extra for that visual appeal. Ha! Then again, if function is all that matters to you, then you can skip this little factor. I must say, mine is pretty sleek.

Purpose

Lastly, why do you need or want an air purifier? What are you wanting to clean out of the air? What symptoms are you wanting to lessen? Knowing the answers to these questions will help you choose an air purifier that does what you need it to do. It’s pointless buying a highly recommended air purifier if it doesn’t meet your needs.

Features to Consider

Alright, we’re in the home stretch! Here are some features to consider when getting a portable air purifier. Bear in mind that not all types of air purifiers have or require these features. These are mostly when considering filter-based units.

Fan

Air purifiers with fans are more efficient than those without. There are exceptions to this though, such as the TSS Thermodynamic Sterilization devices that don’t need fans.

Handle

A handle is helpful if you’re wanting to move the unit around, or even just pull it out of the way.

Speed Dial

Does it have a speed dial where you can select various speeds? Especially when there’s a fan, it will effect the ACH as well as noise levels.

Remote

Is it important for you to be able to remotely control your unit? Some even have apps for your phone from which to control them.

Servicing Indicator

Some units have an indicator that alerts you when it’s time to service the unit, replace or clean the filter.

Dirt Sensor

Some air cleaners have a sensor that measures how polluted the air is. If it senses the air is more polluted, it will adjust the fan speed to move the air quicker for cleaning.

Program Timer

Some air purifiers can be programmed to only operate at certain times.

Washable Pre-filter

Some HEPA air cleaning units come with washable or vacuum-able pre-filters, a great help in extending the lifespan of your HEPA filter.

Air Purifier Common Terms

MERV

Minimum efficiency reporting value (MERV), developed by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). MERV rates the efficiency of air filters. For example, a filter at MERV 14 or above will remove airborne particles 0.3 microns or larger. A high efficiency MERV 14 filter can remove 75% of 0.3 µm particles. The top performing filters typically have a MERV higher than 10. A MERV 16 filter captures more than 95% of particles.

MPR

If you use a Filtrete filter by 3M, you’ll notice another rating system on their products – namely a MPR rating. MPR stands for Microparticle Performance Rating and was developed by 3M to rate an air filter’s ability to capture the smallest airborne particles. MPR is different from MERV, the Minimum Efficiency Reporting Value. The MERV system measures a filter’s ability to capture large particles. The MPR only takes into account the microscopic particles between 0.3 and 1 µm.

CADR

Clean Air Delivery Rate (CADR) measures the speed at which an air purifier cleans the air. A  CADR above 350 is considered excellent, a CADR below 100 is poor. Room size is to be factored in, as a CADR of 100 will be provide sufficient cleaning for a room that is 155 square feet.

ASHRAE

American Society of Heating, Refrigerating, and Air-Conditioning Engineers

AHAM

The Association of Home Appliance Manufacturers certifies most room models as part of a voluntary program that includes appropriate room size and maximum CADR.

HVAC

Heating, Ventilation and Air Conditioning – central air systems.

HEPA

High-Efficiency Particulate Arrestance filters

Micrometer (µm)

Micrometer (μm) is a metric measurement unit of length, also known as a micron. 1 micrometer = 0.001 millimeters.

Decibels (dB)

The measure of how much noise an air purifier emits along with the ‘A’ factor (the account of human hearing on the sound). A regular air purifier on low sits at about 36 dB(A) and a good air purifier at about 32 dB(A). Considering that whispering is at 20 dB(A) and your fridge at 50 dB(A), you can start to get an idea of what the noise level is.

VOCs

Volatile Organic Compounds are both man-made and naturally occurring. They become airborne at room temperature and can pose health risks, especially over extended periods of time.

Sick Building Syndrome (SBS)

Sick Building Syndrome is the term used to describe the adverse health effects that result from poor air quality in buildings. Often the result of flaws in the HVAC unit, off-gassing from materials or other reasons.