How can air filters control indoor pollution?

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One Particle at a Time: An Examination on How Air Filters Can Control Indoor Pollution

Good science is about using evidence, data, and hard facts to make assessments about our reality. It’s not perfect, but with enough peer review on each finding, we have been able to discover core truths about our world that would have otherwise remained a mystery.

One of those truths is the growth in both quantity and severity of air pollution. Just two hundred and fifty years ago, smog in the world’s major cities was virtually unheard of.  Only the areas around the largest mines and refineries were truly polluted.  In the cities, where horses were the only source of transportation and oil had yet to be refined en masse, the air was vastly cleaner than it is today.

The industrial revolution, the rise of oil and coal as fuel, and the introduction of toxic chemicals have led to a sharp decrease in the average safety of the air around us.  In China, for example, air pollution is leading to almost a million premature deaths per year.  

Air pollution has been getting slightly better over the years, thanks to regulations on emissions from vehicles and factories, along with key innovations in emissions control and renewable energy.  But there’s another factor in the control of air pollution that few things about – air purification.

Earlier this year, Delhi installed a 20 foot tall air purification tower in its popular Lajpat Nagar market.  The tower draws in air, cleans it, and then distributes it back into the market.  The visitors to this market enjoy cleaner smelling air, and lower risk of lung damage and disease as a direct result of the construction of the tower.  Similar towers have been built, or are being planned, all over the world.  Air purification on a large scale is a practical method for clearing up our air and returning it to its natural state.

But what about air purification on a small scale?  Most people have a form of air filtration in their homes that they completely forget about.  If you have a home HVAC system, your AC is filtered constantly through the air filter, giving you cleaner air as you go about your day.  All of the air that is in your house right now was once air from outside.  This means that, when you open a door or window, polluted outside air is getting into your home.  Contaminants can even be tracked in with clothing and shoes.  Scented candles, cooking, and dust also contribute to the pollution in your home.

This means your air indoor can be just as polluted as the air outside.  In fact, studies have shown that can be even more polluted, since contaminants can get trapped and concentrated more easily.  There’s evidence that air pollution indoors is around 2 to 5 times more severe than pollution outside, with some homes (particularly those with smokers) showing pollution levels of 100 times the safe outdoor limit.

How can we counteract this?  How can we protect our family’s lungs from harmful chemicals and smog?

The easiest and cheapest answer is to invest in a higher-grade air filter.  Air filters are ranked by their MERV rating.  MERV, or Minimum Efficiency Reporting Value, is a number that measures how effective a filter is at grabbing small particles.

A MERV of 1 to 4 characterizes a filter which can only trap 20% of particles with a diameter of fewer than 10 microns.  A MERV of 8 can trap around 70% of those particles.

MERV 11s are a sweet spot, balancing cost with effectiveness.  They trap about 85% of particles smaller than 10 microns in diameter.

For those with more sensitive lungs, a MERV of 14 can filter out 90% of particles under 3 microns in diameter.

For specialized clean rooms, Ultra Low Particulate Air Filters with MERVs of 20 or higher filter out 99.99997% of particles smaller than 1 micron in diameter.

Indoor air pollution usually consists of smoke particles and aromatic particles.  In order to combat it, you’ll need a MERV of at least 13, which can easily be purchased and delivered from air filter stores like Filter King.  Prices vary by store, but you can expect to spend around $30 or $40.  Buying in bulk, as with most things, gives you a cheaper per unit price.

But a high MERV number is only half the battle when fighting your indoor air pollution.  The other half is the frequency with which your air is cycled through the fitler.  The best MERV in the world does nothing if no air goes through it.

We measure air movement with cycles per hour, which is calculated by dividing the volume of air an HVAC system is passing through itself by the volume of air in a given room.

The higher number of air cycles per hour, or ACH, the cleaner your air will be.  If you can sacrifice some electricity, leaving your AC on higher and longer will help reduce the amount of pollution in your home.

It also helps to turn on your fans, which will mix the air in your home and prevent one area from trapping contaminants.

Pollution is bad, both inside and out.  Outdoor pollution can be fixed with technical innovation and regulation.  But indoor pollution is something each individual must focus on in their own home.  By buying a better filter and allowing your air to cycle more continuously, you make the active decision to protect your family and guests from harmful contaminants.

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