Did you know that more than three billion people still cook with solid fuels like wood, charcoal and coal? Of those who use such fuel sources indoors, over four million of them die prematurely due to overexposure to harmful pollutants. Improving indoor ventilation could markedly reduce this fatality count worldwide.
Cooking appliances in most first-world countries no longer rely on solid fuels; however, this does not make their exhausts less harmful. For instance, gas stoves introduce pollutants like nitrogen dioxide and carbon monoxide into the home. In fact, a recent study in California found that sixty percent of homeowners who cook with gas stoves at least once a week generate indoor pollution levels that exceed federal outdoor standards.
Improving Ventilation in the Kitchen
Gas stoves emit more fine pollutants than electric burners, but both contribute to indoor air pollution in some way. Moreover, the different cooking methods produce different levels of pollution. Frying, for instance, is known to produce the finest particles.
To suck up pollutants at the source, your kitchen should have a range hood above the stove. When cooking, set its fan to the highest setting. That said, it must connect with the outside; otherwise, you are simply recycling air back into the home.
For further protection against indoor pollution, you should also consider an air purification system. Also called an air cleaner, this system removes small particles from the air to prevent them from entering and potentially disrupting your cardiovascular, circulatory and respiratory systems. There are various kinds of air cleaners—large systems that connect to existing HVAC hardware and small, portable machines—so do some research based on your budget and space size before buying a system.
Construction standards ensure that homes today are airtight. While great from an efficiency standpoint, the lack of exchange between inside and outside air poses several problems. The largest concern is air quality.
Like the outdoors, there are various pollutants in our homes. These come from numerous sources, including the things we cook and clean with. If no air can escape, then this means these pollutants can accumulate and become quite potent.
While opening a window or door can let some pollutants out, doing so allows any generated heat or coolness to escape too. This is where air exchangers come in: they mediate the exchange of indoor and outdoor air, conserving some of the heating and cooling in the process.
How Air Exchangers Work
Air exchangers, known also as mechanical ventilation systems, remove moisture and toxins from the home and provide fresh, pre-heated/cooled air. They draw in and exhaust air simultaneously using fans and air ducts. During the exchange, these machines transfer heat from the outgoing stream to the incoming one. They do so without mixing them, as this would contaminate the new air.
Mechanical ventilation systems come in two forms: Heat Recovery Ventilators (HRV) and Energy Recovery Ventilators (ERV). Both can recover anywhere between 50% and 95% of the heat in air expelled from the home. The chief difference is that ERVs can recoup moisture between the two airstreams, called latent heat. This makes it useful when dehumidification is required.
ERVs require different components to conserve latent heat and are often more expensive. Depending on the climate, HRVs are typically sufficient. Places that experience dry, warm seasons are more in need of ERVs than those homes in temperate climates.
An air purifier that exchanges air two to eight times an hour can reduce indoor pollution by more than 80 percent. Of course, its efficacy depends on various factors, including placement and room size.
Unless you buy a purifier that connects to your existing HVAC system, you will need to choose a room for the unit. Most homeowners prefer the bedroom, kitchen or bathroom (or all three). The reasoning: you spend the most time in your bedroom while the kitchen and bathroom have the greatest amount of bacteria.
Regardless which room you choose, there are other placement strategies to consider.
Location of Contaminant
Ideally, the air purifier should reside closest to the source of the pollution. For example, besides the household smoker’s favourite chair. The nearer the source, the earlier it will trap the particles.
Interestingly, placing a purifier by the door can catch the particles before they enter the room. Such a placement benefits households with allergens most. For instance, if you’re semi-allergic to cats but own one anyway, you can place a purifier by your bedroom door to stop dander from floating into the sleeping area.
Airflow and Circulation
An air purifier sucks from the front. If placed near furniture or some other obstruction, it cannot draw in the pollution. That said, the centre of a room is not a good spot either.
Because of diffusion, the best spot for an air purifier is to the side of a room (whichever is most open). The principle of diffusion dictates that particles will spread across the room at an equal distance from one another. Thus, as the machine intakes air, the particles will naturally start to fill in the gaps. As it pushes clean air out, it will create airflow. If placed in the middle of a room, creating such circulation would be more difficult.
Any homeowner with pets knows that animals make a mess. This goes beyond the occasional accident inside or toys littered across the floor. Domestic pets like dogs and cats shed fur, making cleaning a top priority. But fur isn’t the real problem: it’s the dander discarded with it.
Dander—tiny flecks of skin—floats around the home freely, wreaking havoc on our respiratory systems. The allergen survives for weeks, much longer than most other airborne contaminates. Its lifespan allows it to spread throughout the home and cling to furniture. While vacuuming can eliminate it once settled, an air purification system is the only way to strip it from the air.
Not all air purifiers cleanse dander. Specifically, HEPA (high-efficiency particulate air) filters are for catching such fine airborne pollutants. These mesh traps tout more than a 99% efficacy rating!
Air Purifiers for Pet Odors
If dander isn’t an issue, then the smell will be. Pets leave odours in the home that affect air quality. While the HEPA filter targets dander, there are other criteria for odour removal. In particular, the CARD (Clean Air Delivery Rate) of the machine.
CARD measures the volume of air sucked into the purifier and the percentage of particles removed. The CARD factors in particles associated with gases, fumes and odours. Thus, just looking at the air exchange rate of a purifier is not enough; one that simply recycles will only preserve those particles contributing to the smell.
For destroying bacteria and other airborne contaminants, some purifiers emit ozone. While beneficial to indoor air quality, purifiers with oxidizers can be harmful to rodents and birds. In fact, too much pure oxygen can potentially kill them—a reason why the FDA caps air cleaner ozone emissions. For safety reasons, purifiers are best kept away from cages and crates.
For many homeowners, leaving the windows ajar solves their indoor air quality concerns. Doing so brings in a draft of fresh air, letting all indoor pollutants escape. Unfortunately, this is not as effective as people think.
Open windows sometimes introduce new pollutants and allergens into the home. Windows lack the purification mechanics used to mediate the exchange of air. But even if the outdoor air blew in clean, there are other insufficiencies that make it unreliable at improving indoor air quality.
Loss of Heating and Cooling
In the summer and winter months, opening the windows can be costly. If you spend money on heating and cooling, then cracking the windows will let that generated warmth and coolness out.
To create an effective air exchange with open windows, you need to create a cross-breeze. This involves opening several windows—preferably on separate sides of the home. With only a single window, the warm air moves in through the top and cycles cold air out the bottom, benefiting only spaces close to that window. A cross-breeze extends the reach of this exchange; however, the air flow pattern created is somewhat linear. Consequently, much of the stale air stays in the home.
For lasting improvements to indoor air quality, you need activated oxygen, called ozone. Ozone purifies lingering chemicals and odours, but it only lasts between five and 20 minutes. Even a strong inbound breeze cannot generate sufficient ozone to serve as a sustainable solution. Air exchangers, on the other hand, work constantly to produce ozone, creating an ever-fresh indoor environment.