Breathe safely indoors

Most people think air pollution applies only to outdoor air.

But the air inside your home and workspace could be two to five times more polluted than the air you are breathing outside.

We Canadians spend approximately 90 per cent of our time inside. And most of us are not aware of the effects poor indoor air quality can have on our health.

Toxic substances, introduced to your home, go unseen. And yet they pose the single greatest threat to our daily health.

A typical home today contains more than 60 toxic biological and non-biological chemicals. These are caused by such things as household cleaning products, personal care products; carpets, furniture, smoking and cooking.

And then there is pollen, mold spores, pet dander, dust mites, dead skin that falls off the body of humans and pets; bacteria, viruses, radon, and the dust that is generated in renovations.

To make things worse, high humidity levels promote mould growth. A lack of ventilation, especially in air-tight buildings, effectively seal in these toxic things and impact the air inside your house.

Not surprisingly, these substances can sometimes lead to nasal congestion, itchy eyes, sore throat, nausea, headaches, and fatigue. In more severe situations, they can lead to serious health issues such as allergies, asthma, emphysema, bronchitis. In extreme cases, high levels of radon can be a cause of lung cancer.

There are three categories of indoor air pollution:

  • Particulate
  • Volatile organic compounds
  • Biological


These most harmful particles are so small you can’t even see them. They can penetrate and lodge deep in your respiratory system, causing discomfort and eventually leading to illness.

Volatile organic compounds (VOCs)

VOCs consist of chemicals in the gas phase when gases are released from things like cleaning products, furniture, carpets, paint, plastics and so on. When these chemicals react with each other, new compounds are formed.


Living organisms such as bacteria, dust mites and viruses are very small, but they can be debilitating when they cause illness. Mould and fungus, when inhaled into your body, can also wreak havoc.

That’s the bad news. The good news is that just as you are unique, so is your home environment. You can improve its indoor air quality using a number of methods involving proper ventilation, reducing sources of indoor pollution and – very important – checking your furnace filter at regular intervals.

Furnace filters can make a big difference, but not if you have the standard kind. Standard filters do not generally clean the air in your home or improve air quality, except from airborne particles. The main purpose of your furnace filter is to protect the blower fan and the air conditioner evaporator coil from dust and other airborne particles that enter the return air systems. A furnace filter also helps to remove air particles and prevent other contaminants from being re-circulated.

Choose the right furnace filter

Trying to choose the optimum furnace filter is not an easy task. Take a walk down the aisle of your typical big box store and you’ll come across more than 100 varieties.

Here are some tips to help you:

  • Check the physical size of the existing filter compartment on the return air side of your furnace to determine the dimensions of the filter.
  • Choose the appropriate Minimum Efficiency Reporting Value (MERV) rating for your filter. MERV is a standard that rates the overall effectiveness of air filters. Higher MERV ratings equate to finer filtration, meaning fewer dust particles and other airborne contaminants can pass right through the filter. MERV ratings range from 1 to 20. Ratings 8 to 13 are typically used in homes. Ratings 14 to 20 are normally found in hospitals and operating rooms. Filters with higher MERV ratings need to be changed more often to avoid restricted air flow that can drain efficiency or possibly damage your system. (Check your furnace manual to find out what MERV rating is allowed.)
  • When we’re working in a dusty environment, we usually wear a mask to protect our lungs. We replace it as it gets clogged. Your furnace filter should be treated the same way. As your furnace filters become more and more clogged, the space for air flow through it is reduced. The result with this weak air flow is a high energy bill while your HVAC works harder to provide the same amount of heating or cooling. This could result in premature failure of your systems.
  • Your furnace filter is like a trash can, storing more and more particles. If you don’t change it, imagine yourself breathing the air that passes through a filthy trash can. Buy filters in bulk. (That will help remove excuses for not changing them.) Check them each month and replace them about every 90 days. Hint: If you can’t see light through your filter, it’s time to replace it.

Good ventilation is another solution to indoor air quality. You might think this is just a matter of opening your windows and doors, or perhaps running your kitchen and bathroom exhaust fan. However, in winter this is ineffective because it’s difficult to control humidity levels. It’s also uncomfortable (in winter) with open windows, and a waste of energy.

A heat recovery ventilator (HRV) – or better yet, an energy recovery ventilator (ERV) – drastically improves your indoor air quality and controls humidity levels at the same time. These systems offer a controlled method for ventilating a home and also minimizing energy loss. During the winter, warm inside air is exhausted to the fresh, cold supply air in order to warm it; and during the summer, cold inside air is exposed to the warm supply air in order to cool it. An ERV’s heat exchanger transfers water vapour along with the heat, thereby controlling humidity. An HRV only transfers heat.

There are air purifiers that don’t require ventilation.

HEPA (High Efficiency Particulate Arrestance) is a filtration standard created by the US Atomic Energy Commission. To qualify as a HEPA filter, a media must be 99.97% efficient at removing particles the size of 0.3 microns. HEPA filters have become widely used in medical environments, homes, aerospace, computer chip manufacturing and electronics, vacuum cleaners, vehicles and airlines.

If you’d like this system installed in your home using a bypass method, speak to your HVAC contractor. In homes that require higher indoor air quality, the systems are normally installed with three sets of filters to remove particles and VOCs simultaneously.

It operates in stages.

In stage one, the inexpensive pre-filter, usually foam, removes larger particles from the air and helps prolong the life of the HEPA filter.

In stage two, the HEPA filter removes 99.97 per cent of particles 0.3 microns or larger. It can also remove things like pollen, mould spores, pet dander, bacteria, and viruses as well as small air particles.

In stage three, the carbon filter removes VOC chemicals such as odours.

If you’re not sure of your home’s indoor air quality, it would be a wise idea to have it tested. Speak to your HVAC contractor to review an install the ventilation system that is best suited to your home.

For more information, visit these websites:

Roy Nandram is president of RND Construction Ltd.