Air Exchanging for Health

by Kim Kinrade

Many people are astounded to hear that one of the most dangerous air quality areas in the world is right in the home. Like a smog-filled atmosphere the air in a home can get loaded with dust, bacteria, mold spores and insects.

Since mankind went indoors for shelter from the elements air quality has been a major concern. Smoke from the fires was breathed by the inhabitants of caves who also never knew that the fires also burned up oxygen in the contained space, as well. Chimneys solved this problem and it was probably noticed that the working fire needed air movement to keep the flames going. As people moved into homes and became more efficient at sealing them from the elements the indoor air quality began to get steadily worse.

Unlike commercial structures, few residential air ventilation systems have automated systems and so air quality is left up to the people who know the least about it: the homeowners. New construction these days is very tight so that air exchange happens mostly through opening doors,bathroom exhaust fans and, in warmer times, windows. In other words ventilation is far from an automatic process- it is haphazard at best.

Ventilation Methods

Supply-Fan System

This method, where air is blown into the home, is very common and the homeowner can decide the source of the air intake. Because it pressurizes the home there is no worries about backdrafting from fireplaces or from moisture coming from bathroom areas. The outlet should be placed in a central location to avoid the distribution of pollutants from kitchens or bathrooms. The downside is that unless there is a first-rate filtering system dust, pollen, spores and insects can get sucked into the home. In wet areas this system can also fill the home with moist air causing condensation and rot.

Exhaust-Fan System

This method, where air is sucked out of the home, is good for wet parts of the country as it does not allow moisture to get in. Some homeowners use continuous, but ultra-quiet, bathroom fans as the exhaust source. One of the drawbacks to this system is that, if not balanced properly, there could be negative air pressure in the home. This is bad for the oxygen content in the home and can also cause backdrafts in fireplaces. As well, the intake port should be placed in an area where pollutants and allergens are not present.

Air Exchange System �

In modern homes energy efficiency is the mantra which means the homes are getting more air-tight. This, of course, not only means that the home stays warmer but also no fresh air gets in and no stale, moisture-laden air can get out. This is why many building codes demand that indoor air pollution and humidity be controlled with a mechanical ventilation installed when the structure is built. The ventilation system is not expensive to run. A small, quiet fan continuously ventilates the entire home. � New R-2000 homes are equipped with air exchangers and these are available in many styles and models but they operate in two basic ways:

1. Heat Recovery Ventilator (HRV): A heat recovery ventilator is also known as an air exchanger. The ways it works is that fan-driven unity brings the outdoor air, which is usually cold, through a core which is being warmed with stale air that is being exhausted. The core is made from thin, moisture-proof propylene cells accept heat from exhausted air and transfer it to the incoming, fresh air, thereby creating a great energy saving. It also takes out excess humidity which can cause health problems and moisture damage to window frames and doors. It has been shown that over 90%

2. Energy Recovery Ventilator (ERV):This differs from the HRV in that it transfers both heat and moisture from the intake to the exhaust streams, and vice versa, to equalize humidity levels.

Air Filtration Systems

It doesn't matter what kind of a ventilation and moisture-reducing system you have if pollutants are still allowed in. This is where the new filtration systems come in. Early systems were a fiberglass batt design which trapped most of the dust but let small particles � even fiberglass from the batts � get into the air supply. Today there are many systems which can improve air quality.

1. HEPA (High Efficiency Particulate Air) Filters:These are the standard filter as they use today and for good reason. HEPA filters were invented by scientist working on the atomic bomb to trap radioactive particles. They are rated to remove at least 99% of airborne particles as little as 0.3 micrometers in diameter � which is really tiny! The filter works by by forced air which slams particles into fibers where adhere until it is time for cleaning.

2. Electronic Filters: Most of this type uses a technology called �electrostatic attraction� to grab charged particles. Offensive particles are charged by being put in a flow of ionized air where they accumulate on flat collector plates which are oppositely charged. These plates can be cleaned in a dishwasher.

3. Gas Filters: These filters are more for places where smells are prevalent, like commercial operations. They take out offensive gas smells by charcoal filters and other processes. Most new homes have a hybrid HEPA and electrostatic filter for the best protection. These are best installed in a new home but can also be added onto older ones.