Air Purifiers For Asthma: Which Type Works Best

When considering which are the best air purifiers for asthma, it's important to understand which air problems can trigger an asthma attack so that you know exactly what you want to eliminate.

Common allergens which can be suspended in airborne dust are pollen, mold spores, animal skin and hair, together with dust mite and cockroach body parts and excretions.

Other airborne irritants are gases (particularly ozone and sulfur dioxide) as well as strong smells including paint, perfume and cooking fumes.

Air purifiers for asthma are designed to remove either particles, as in the first category or gases and fumes as in the second category, but not both because they operate in different ways.

Before investing in an asthma air purifier, normal allergy cleaning procedures should be pursued ( see Allergy? Dust Mites Could Be to Blame), and obvious sources of strong smells such as perfumes should be dealt with.

All particulate air cleaning devices rely on the unwanted particles being suspended in the air. This may seem obvious, but heavier particles settle quickly and only get re-suspended when they're disturbed which may not be close enough to an air cleaner to trap them before they settle again.

Air Purifiers for Asthma: Ozone Generators

Ozone is an unstable gas which is how it can freshen air. It has three atoms of oxygen, one of which will attach itself to particles in the air and oxidise them, leaving the other two as oxygen.

As seen above, ozone is a lung and respiratory tract irritant. If you can smell it, it can be dangerous. If you can't smell it, it's probably not being produced in sufficient quantity to have an effect on the air quality.

Not suitable for asthma sufferers.

Air Purifiers for Asthma: Ionizers

Ion generators work by discharging ions into the air, which attach themselves to airborne particles and give them an electrical charge. This makes the particles stick to walls, curtains and our lungs.

Sure, the air becomes cleaner, but these particles are still around and can easily be disturbed and become airborne again.

So, not only are the particles still present, but they can be attracted to our lungs. The other thing is that ionizers often produce ozone, (see above), which again makes them unsuitable for asthmatics.

Air Purifiers for Asthma: Electrostatic Precipitators

Electrostatic Precipitators work like ionizers, but instead of firing the ions into the air, they collect the charged dust particles onto negatively charged collector plates.

This method effectively removes dust particles from the environment.

Drawbacks are that they only work with a low speed airflow. Higher speeds blast the particles straight past the collector plates.

As the collecting plates get filled up with particles, the efficiency of the unit decreases. The collector plates have to be cleaned regularly for the unit to remain effective.

These units can also produce ozone.

Air Purifiers for Asthma: UVGI Cleaners

Here's a mouthful. UVGI means ultra violet germicidal irradiation. UV light at certain frequencies can alter the DNA of bacteria, viruses and some molds, rendering them incapable of reproduction. This system is best used inside HVAC ducting where the light will be shielded.

The frequencies used by ultra violet lights in UVGI do not produce ozone.

Not effective against dust mite and mold allergens but good for stopping the growth of mold in HVAC systems.

Air Purifiers for Asthma: PCO Cleaners

Another mouthful. PCO means photocatalytic oxidation. PCO air cleaners are meant to change gases into harmless by-products. The use ultra-violet light and a catalyst that reacts with ultra violet.

The by-products of PCO cleaners can also be irritant to asthma sufferers, and these air cleaners are not designed to remove particles.

Air Incinerators

Domestic examples of air incinerator purifiers are virtually useless because they have no fan, relying on convection of the heated air to move it through the ceramic element that heats the air.

Air is moved in extremely small volumes.

Air Purifiers for Asthma: Air Filters

For air filters to work, the particles to be filtered must be suspended in the air. This may seem obvious, but heavier particles settle quickly and only get re-suspended when they're disturbed which may not be close enough to a filter to trap them before they settle again.

Filter Ratings (MERV)

Air filters are rated by MERV (Minimum Efficiency Reporting Value) from 1, low efficiency, to 20, which is the highest HEPA rating. HEPA means 'high efficiency particulate arrestance'.

As you go up through the MERV ratings, efficiency at collecting smaller and smaller particles increases, but so does resistance to airflow which means that you need more powerful fans to drive the air through.

MERV 1 - 4
These are flat panel filters up to an inch thick. For collecting larger particles, they are used in HVAC systems to protect heat exchangers and fans. They are also used in front of higher efficiency filters to stop them clogging up too quickly.

MERV 5 - 8
These are extended surface filters, either pleated or multi-fiber. Depending on the construction, it's possible to get increased efficiency without impacting too much on airflow.

These filters will remove particles of sizes from three to ten microns, which includes animal skin flakes, saliva and urine, dust mite body parts and waste, as well as mold spores.

MERV 9 - 13
More extended surface filters, used for eliminating particles from one to three microns in size such as auto emission particles and humidifier dust.

MERV 14 - 16
These are high efficiency filters with more resistance to airflow. they will take out particles from 0.3 to one micron in size such as sneeze droplets and most smoke particles

MERV 17 - 20

Here we enter the area of the true HEPA filter, with a high resistance to airflow. They can remove particles as small as 0.1 micron such as viruses and smoke.

There is a balance to be made between efficiency and airflow. HEPA filters need powerful fans to create a pressure gradient great enough to get air through them.

Similar effectiveness can be achieved by using a filter with a MERV rating of twelve to thirteen, because more air can be moved through them.

Installing a HEPA filter in an HVAC system will probably mean that larger and noisier motors will have to be installed.

Beware of filters that use an electrostatic charge to increase their effectiveness. This charge will degrade with time.

Portable Air Cleaners

Portable air cleaners can use the technologies above, or a combination of them.

Air Purifiers for Asthma: Conclusions

Electrostatic precipitators can work well, but are usually not high airflow units because particles need to move fairly slowly to allow them to be caught on the collector plates.

These collector plates will need cleaning at regular intervals to maintain the effectiveness of the unit. The amount of ozone produced by individual models varies. Check before you buy.

The bottom line is that it's hard to beat an efficient air filter system in conjunction with a steam cleaner to get the particles that are not airborne.

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