Indoor Air Quality 101
Selecting the Right Approach
What's the best way to clear the air in your facility? The right approach to indoor air quality (IAQ) depends on the applications you are using, the amount of dust or fumes generated, the specific health and safety risks of your particulate, and the layout and characteristics of your facility.
There are four basic approaches to indoor air quality for industrial facilities:
Filtration vs. Exhaust
The first choice you have to make is between a filtration system and an exhaust system.
- In an exhaust system, contaminated air is simply captured and exhausted outside of the facility. This is generally done using a ventilation system with large fans that pull dirty air out and exhaust it to the outside, often through the roof. A make-up air unit is required to return clean outdoor air to the facility and avoid creating negative air pressure inside the building.
- In a filtration system, dirty air is pulled into a collector and through a series of filters. The filters remove particulate from the air. Clean air can then be returned to the facility.
A simple exhaust and make-up air ventilation system is the cheapest and easiest to install. If you only need ventilation to clear the air after occasional “dirty work,” this may be the right approach for you. However, if your industrial processes generate large amounts of dust and fumes on a regular and ongoing basis, filtration may be a better option. Filtration systems offer several advantages:
- Lower energy costs: Exhaust and make-up air systems push out air that has been heated or cooled to indoor temperatures and pull in outdoor air that must then be heated or cooled all over again. Over time, this can be a huge drain on your energy bills.
- Environmental compliance: Blowing contaminated air into the environment may put your facility out of environmental compliance. The U.S. Environmental Protection Agency (EPA) is cracking down on outdoor emissions from industrial applications, as are other regulatory bodies in North America and Europe. If your processes produce emissions containing toxins such as manganese, beryllium or hexavalent chromium (all common byproducts of welding), or other pollutants of concern such as crystalline silica or carbon black, you need filtration to keep them out of your local environment and avoid potential fines.
- Cleaner rooftops: Blackened roofs often provide visible evidence of pollution around exhaust systems. Increasingly, community members and regulatory bodies are finding that evidence through photographs on Google Earth.
- Cleaner grounds: What happens to pollutants that are exhausted to the outside? While some are carried away by the wind, many settle back down in the immediate vicinity. Some may even be pulled right back in through the make-up air unit. If you are exhausting a large volume of particulate, it will settle on cars in the parking lot and outdoor walkways, where employees will carry it home or back into the facility on shoes and clothing. For some types of dust, this may only present an annoyance. However, if your particulates are toxic, this can be a significant concern.
Ambient vs. Source Capture
The second major consideration is ambient vs. source capture.
- Ambient systems are centralized whole-facility solutions. They continually clean and turn over air from the entire building.
- Source capture systems are point solutions. They capture fumes and particulates at their source to prevent them from propagating throughout the facility.
The choice between source capture and ambient filtration depends on the type and volume of fumes you are producing as well as the physical constraints in your building. If you are generating significant volumes of dangerous fumes, such as from robotic welding, in most cases it is preferable to capture them as close to the source as possible. Source capture reduces the amount of fumes that workers will breath in both near the fume-generating process and throughout the facility as a whole. Hoods, fume arms, backdraft tables and fumes guns collect dangerous fumes and particulate as they are created.
However, source capture is not always possible. The size of parts being worked on and physical constraints such as overhead cranes may make source capture difficult to implement. In these cases, an ambient system combined with personal protective gear for workers closest to the fume-generating processes may be the best option. Ambient may also be a viable option for facilities that produce lower volumes of particulates throughout the facility rather than large volumes contained in specific areas.
Many facilities use a combination of source capture and ambient systems. Depending on the system selected and the application it is used for, a correctly used source capture system will collect between 70%-90% of fumes. This may have been enough in the past, but tightening air quality regulations and an increased awareness of health hazards are prompting many companies to add an ambient system to collect fumes and particulates that source capture may miss. A secondary ambient system can be especially helpful in the following situations:
- Welding large equipment that requires welders to move around the pieces they are welding.
- Relying on manually positioned fume arms while welding large parts.
- Utilizing open smoking bins where freshly welded parts are allowed to cool.