When property owners are considering upgrades for their HVAC systems, plenty of attention is given to energy savings. However, providing healthy conditions for occupants is also very important. There is a common misconception that indoor air quality costs extra energy, but you can achieve both efficiency and air quality with the right design choices.
Although there are many types of air pollutants, the US Environmental Protection Agency gives special attention to seven: carbon monoxide, lead, nitrogen dioxide, ozone, coarse particulate matter, fine particulate matter and sulfur dioxide. This article will provide a brief overview of each pollutant, focusing on their main sources and effects.
All the pollutants described in this article are actively monitored by the US EPA, but this only applies for outdoor air. If you are a property owner, you are responsible for keeping indoor pollutant levels under control, but there should be no major issues of your ventilation systems and combustion appliances are designed properly.
Carbon monoxide (CO) is a combustion product, and it should not be confused with carbon dioxide (CO2), which is much less dangerous. While CO2 only becomes lethal for humans at concentrations close to 100,000 ppm (10%), CO causes instant loss of consciousness and death within minutes at only 10,000 ppm (1%), and any concentration above 1,000 ppm (0.1%) is lethal in just a few hours. What makes carbon monoxide so dangerous is its lack of color, smell or taste, making it impossible for humans to detect. However, at low concentrations it produces less severe reactions like headache and nausea, so you must react fast if several people experience these symptoms at once.
Thankfully, CO monitors are affordable. Also consider that combustion is the main source, so you can minimize the risk of exposure by making sure all combustion appliances are properly vented. The Occupational Safety and Health Administration (OSHA) limits CO exposure to 35 ppm for a typical 8-hour workday.
Lead (Pb) is an extremely harmful substance for humans, affecting several major organs in the human body, and causing developmental issues for children. Its main sources in urban settings are paint and gasoline, but stringent legislation has been effective in reducing its levels. However, waste incineration, mining, and battery manufacturing are still significant sources of lead pollution.
Nitrogen dioxide (NO2) is a combustion product characterized by its pungent odor and reddish coloration. It main effect is respiratory system irritation, and long-term exposure can lead to asthma, or worsen its symptoms in individuals already suffering from the condition.
Motor vehicles are among the main sources of NO2 in urban settings, so make sure that enclosed parking areas have adequate ventilation to minimize exposure. Another simple measure to keep this gas out of indoor spaces is closing the windows during high traffic. The US EPA monitors outdoor air quality for mayor cities and provides live data in their site, where you can check the condition of outdoor air before opening the windows.
Other than vehicles, backup generators are a main source of NO2 in building interiors, hence the importance of adequate flue design.
Ozone is beneficial for humans when located high above in the atmosphere, since it helps block harmful radiation from outer space. However, the story is different when ozone is found at ground level, where it has negative health effects. Exposure to ozone causes severe irritation of the respiratory system, with symptoms such as chest pain, shortness of breath, coughing and inflammation. Patients with asthma or bronchitis can experience a worsening of their symptoms upon exposure to ozone.
Be especially careful when selecting air filters: some models use ionization to capture and remove pollutants from indoor air, but also create and release ozone in the process. In other words, they replace one harmful substance with another, so other options are preferable.
Coarse and Fine Particulate Matter
Particulate matter (PM) is a broad term that describes suspended particles and droplets, which have a series of negative health effects. For example, smoke and soot are both considered PM.
Coarse particulate matter is that with a maximum diameter of 10 microns (PM10), while fine particulate matter has a diameter below 2.5 microns (PM2.5). Both types can be inhaled by humans, bringing respiratory and cardiovascular health issues, but fine particulate matter is the most harmful due to its small diameter.
Particulate matter can be generated directly, often as a product of fuel combustion or waste incineration, but it can also form from chemical reactions involving other pollutants - ozone, sulfur dioxide and nitrogen dioxide have all be identified as PM precursors.
The NYC Department of Environmental Protection banned fuel oil #4 and #6 in 2011, both of which produce large amounts of fine particulate matter. Before the rule was published, PM2.5 was causing around 3,000 deaths per year in NYC. These heavy heating oils were only being used in 1% of buildings, but were releasing 86% of soot pollution.
Sulfur dioxide (SO2) is a pungent and colorless gas, capable of damaging the human respiratory system in a short time upon exposure. It is a combustion product like carbon monoxide, so the best way prevent exposure is by ensuring that combustion appliances are properly designed, vented and maintained. Since motor vehicles are a main source of SO2 in urban settings, the measures used prevent NO2 exposure also apply here.
Bonus: Volatile Organic Compounds
Although the US EPA does not monitor them actively, volatile organic compounds (VOCs) are among the main indoor air pollutants. These compounds are found in several cleaning products, cosmetics and construction materials, causing respiratory irritation with short-term exposure and more severe health conditions with prolonged exposure. Some VOCs are also generated as combustion products. Monitoring individual VOC concentrations is impractical because there are thousands of them, so their total concentration is generally measured.
VOC concentrations can be kept low by avoiding synthetic fragrances and using natural cleaning products, while ensuring your combustion appliances are well vented. According to NASA, indoor plants are also effective for controlling VOCs - many plant species are capable of metabolizing them, while releasing oxygen.