In the realm of Indoor Air Quality (IAQ), ventilation often takes centre stage. The exchange of indoor air with outdoor air is a simple yet effective method to dilute pollutants and improve overall air quality. However, what happens when the outdoor air itself is compromised? What is its impact on indoor air and what are then the options available to building occupants?
Before delving into solutions, it's crucial to understand the significance of outdoor air quality. While indoor sources of pollution like VOCs, dust, and biological contaminants are well-known, outdoor air can also introduce pollutants such as industrial emissions, vehicle exhaust, wildfires, and even pollen into indoor spaces. These can significantly degrade IAQ.
It all starts with monitoring IAQ so that remedial actions can be taken if it deteriorates, especially when changes in outdoor air quality are not immediately obvious or broadcast by local media.
For those living in areas with varying air quality, monitoring outside Air Quality Indices (AQI) is essential. These provide real-time information on local pollution levels, enabling individuals to make informed decisions about when it's safe to ventilate their indoor spaces or exercise outdoors.
Unfortunately, there are times when opening windows (in person or via automation) for ventilation purposes is undesirable. Extreme weather conditions, such as high temperatures or freezing cold weather, would make this uncomfortable. Additionally, heavy rain, strong winds, or poor outdoor air quality (due to smog, wildfire smoke, etc.) could render bringing in outdoor air ineffective or even harmful unless additional measures are taken.
When outdoor air quality is poor, several strategies can be used to maintain a healthy indoor environment;
1) Energy Efficient Mechanical Ventilation:
Heat Recovery Ventilators (HRVs) or Air-to-Air Heat Exchangers: HRVs are energy-efficient systems that exchange indoor and outdoor air while recovering heat or saving on energy for cooling. This helps maintain a comfortable indoor temperature without compromising air quality.
Balanced Ventilation Systems: These systems provide continuous ventilation by drawing in fresh air from the outside and expelling stale air. They can be equipped with filters to remove pollutants.
2) Air Purifiers:
HEPA Filters: High-Efficiency Particulate Air (HEPA) filters can capture a significant portion of airborne particles, including dust, pollen, and many allergens.
Active Germ Suppression Technology: Some air purifiers utilize additive technologies to 'inoculate' the air and inactivate bacteria and viruses.
3) Filtered Outdoor Air Intake:
Air Intake Filters: These devices can filter outdoor air before introducing it into the building, removing pollutants.
4) Indoor Air Circulation:
Fans: Circulating indoor air can help distribute pollutants more evenly and reduce localized concentrations if there is no choice but to bringing in outdoor air.
Carbon Scrubbers: These remove pollutants like carbon dioxide (CO2), but are very expensive and so are hardly used except for in submarines and space stations.
While outdoor air can significantly impact indoor air, we can still maintain a healthy environment even in challenging conditions. By understanding the factors affecting outdoor air, monitoring the relevant indices, and implementing appropriate strategies, building occupants can create a healthier and more comfortable indoor space.