Did you know indoor air quality on average is two to five times more polluted than outdoor air?

The COVID-19 pandemic has dramatically increased awareness and concern levels about indoor air quality. Suddenly people started worrying about the tiny particles we breathe in, and they also became interested in how air filters protect against these particles and other pollutants.

Camfil has been concerned about this topic for almost fifty years, and we want to help you understand your options for improving indoor air quality.

There are two main types of indoor air pollution control: air filtration and dust collection. While they both have the same main goal of removing harmful particles from air inside buildings and structures, there are key differences.

What is Air Filtration?

Air filtration is the HVAC technology that ensures that the air inside buildings is clean and safe to breathe. Most commercial HVAC systems provide ventilation first and foremost to continually brings fresh air into the building and filter the recirculated air. According to the American Lung Association, the more air circulates, the less chance viruses have to spread.

However, unwanted particles still make their way inside – particles like dust, chemicals, off-gases from new furniture or carpet, or residual fumes from paint, bacteria, viruses, smoke, cooking odors, outdoor pollen, mold and fungi.

These airborne particles are called particulate matter (PM) and are categorized by the World Health Organization (WHO) according to their size. PM1 includes soot and viruses, PM 2.5 includes bacteria, PM 10 includes fine dust and pollen.

The smaller, the particle, the more dangerous it is because it can enter the cells of the body and become trapped there.

There are a wide variety of air filters in use today from the flat panel filters common in most home HVAC systems to large V-bank style and bag filters for commercial applications with high airflow. Regardless of the style, air filters remove contaminants from the air, trapping them within the filter media while allowing the clean air to flow through and into the facility.

The most common type of air filters used in commercial buildings are classified according to the ASHRAE MERV scale. Filters are rated between one and 16 and the higher the number, the more effective the air filter is at removing small particles. During the pandemic, ASHRAE’s Epidemic Task Force recommended that the minimum air filter efficiency installed in an HVAC system to protect publicly accessible spaces should be MERV 13.

HVAC systems are generally designed to remove contaminants from the surrounding ambient air and from human activity occurring within a facility. However, manufacturing and other production processes can create a large volume of dust and contaminant that would overwhelm an HVAC system. In those situations, the only solution is a dedicated dust collection system.

What is Dust Collection?

As discussed above, air filtration systems are used for capturing incidental dust. Facilities that actually create large volumes of dust require dust collection systems. These systems are generally used for capturing PM10 or larger particles.

Dust collectors use suction to gather nuisance and hazardous dust and fume particles from the air before they can settle on surfaces. Each minute, they “ingest” high volumes of dust-laden air from processing area, remove dust and return clean air to either the processing area or outside the facility.

For example, each Gold Series dust collector module moves 5-6,000 CFM of air through the system. Because of the high capacity of these collectors, many facilities use them to keep dust and fumes in check during manufacturing and processing operations.

This protects their workers from toxic and combustible dusts, which is required by major regulatory bodies like Occupational Safety Health Administration, the National Fire Protection Agency and the U.S. Environmental Protection Agency. Facilities must find ways to maintain compliance, and dust collection systems are often the most cost-effective solution.

There are various types of dust collectors that can be configured to fit the needs of your specific operations. Some examples of popular dust collector styles include:

  • Cartridge dust collector: Cartridge dust collectors are industrial dust collectors that use cartridge-style filters to collect and filter dust. When the filters become loaded with dust, the collector automatically cleans them using a pulse of air, sending the dust into a hopper below for disposal. They are ideal for most industrial dust applications.
  • Baghouse dust collector: Similarly, baghouse dust collectors are industrial dust collectors that use long cylindrical bags made from woven fabrics as filters. These are often used in dust-intensive applications like mining.
  • Wet scrubber: Wet scrubbers, also known as air scrubbers, use a liquid (usually water) to remove dust particles from the air. Contaminated air is moved through filters then sent through a mist, which removes particles from the stream. The air then moves through an outlet port and cycles through the system. Wet scrubbers are most often used in applications where the slurry can be reused or repurposed.
  • Portable dust collector: Unit dust collectors are small, portable and ideal for isolated jobs that produce dust. They can be placed strategically to collect dust from the source and can be used either on their own or in conjunction with a larger dust collection system.

Filter Media

A key difference between filtration systems and dust collectors is the filter media used. Filter media is the fabric that is folded into the filter cartridge. HVAC filters can use high-efficiency HEPA filters or filters with activated carbon or UV light because they do not deal with high volumes of dust that would fill the filters quickly.

However, dust collector filters must be able to continually capture and release dust into a hopper to prevent them from getting full and having to be changed out every few minutes.

Dust collector filter media must be chosen based on the type dust being collected, particularly if the dust might be combustible. Industrial dusts are often explosive and have more varying characteristics than nuisance dust. If your dust is explosive or combustible, you are required to have your dust analyzed to determine the safest filter media for your application.

There are two basic factors to consider when specifying dust collector filters: media type and fabrication technology. The base media is generally a nonwoven fabric, but it is often coated with chemicals to provide specific performance properties such as anti-stick, conduction, static dissipation and flame retardance.

Fabrication technology is the way in which the media is folded into the cartridge. For example, Camfil’s HemiPleat®  patented folding technique makes sure that the pleats are uniform across the entire media by applying a plastic bead between the fabric folds to keep the pleats open and exposed to the airstream. This design helps to collect more dust on the filter media and then release it easily during pulse cleaning. This helps maintain airflow, efficiency and a low pressure drop, which is important because installing cartridges with too high an efficiency level for the application will cause filters to clog too quickly, requiring replacement.

MERV Ratings vs. ASHRAE Standard 199

As stated above, MERV (minimum efficiency reporting value) ratings are important when evaluating air filtration, particularly in HVAC applications. They generally signify filters with superior filtration. Filters are rated on a scale of 1 to 16 that corresponds to a filter’s ability to capture particles in the range of 0.3 to 10 microns. Higher MERV ratings correspond to a greater percentage of smaller particles captured on each pass. So, for HVAC filters, a higher MERV rating indicates a more efficient filter.

For dust collectors, MERV ratings are less useful. MERV ratings apply only to new filters and their initial filtration level in a static environment. Since dust collectors manage high volumes of dust over an extended period of time, filters are constantly loading and unloading, so their efficiency level is constantly changing. MERV ratings do not take these fluctuations into account.

When evaluating dust collectors and filters, users should instead consider ASHRAE Standard 199. This test replicates a dust collector’s real-world performance.

The Bottom Line

Both air filters and dust collectors have important roles in maintaining indoor air quality. HVAC systems continually recycle indoor air, while adding in fresh outdoor air and filtering out impurities in buildings were many people work or visit. Dust collectors are required for handling large volumes of dust produced in factories and processing centers…particularly when those dusts tare explosive or toxic to workers or products.

For both of these systems, it is important to select the right filter that will meet the needs of your specific application in order to obtain maximum efficiency and achieve optimum indoor air quality.

When you’re ready to have your facility’s dust controlled in the most cost-effective way possible, our experts are here to help. Our advanced equipment and state-of-the-art dust collection test facility can provide the data you need to avoid guesswork, invest wisely in equipment and keep your team safe. Click here to learn more.