Ensuring high indoor air quality (IAQ) in manufacturing and processing facilities is crucial for safeguarding the health and wellbeing of employees. Poor IAQ can cause symptoms such as headaches, fatigue, and eye irritation, and has also been linked to serious conditions like asthma and cancer.

Research has shown that indoor air quality often falls below that of the outdoors. There are many common factors that can negatively impact IAQ, including:

  • Temperature
  • Humidity
  • Recycled or returned air
  • Mold
  • Vapors
  • Dust created by manufacturing processes
  • Construction materials
  • Airborne chemicals

With manufacturing plants, metalworking shops, and processing facilities becoming increasingly airtight in an effort to conserve energy, pollutants can get trapped and accumulate over time. Facilities that generate dust often employ dust collection systems to remove particles from the air that cannot be addressed by general HVAC filtration.

Air filters play a key role in these dust collection systems by trapping airborne particles such as dust, smoke, and pollen. The efficiency of these filters directly impacts the overall effectiveness of the system in removing particles from the airstream. Therefore, superior filtration can significantly enhance indoor air quality.

One of the key factors to keeping your dust collector operating efficiently over its lifetime is selecting the right dust collector filters. In past blogs, we’ve talked about how to save on dust collector filters and how to choose the right kind of filter media. Nevertheless, understanding the concept of the air-to-cloth ratio is indispensable to determine the most suitable filter for your dust collector.

Selecting a dust collector filter with an inappropriate air-to-cloth ratio may put your workers at risk. An inadequate filtration efficiency may result in increased exposure to particulates, which can potentially trigger various health problems. Similarly, poor dust filtering may create an environment conducive to explosions. Hence, it's crucial to ensure the correct air-to-cloth ratio for your dust collector to protect your workers' health and maintain a safe work environment. Here are a few important things to understand.

Two Industry Methods Evaluate Filter Efficiency

The air filtration needs of a manufacturing or processing facility can vary depending on the size and type of dust contaminants that need to be removed. The most effective filter is one that is specifically designed to efficiently remove a certain type and size of particle matter over time. To aid in the selection of the most suitable air filter, manufacturers can turn to two primary standards:

  • ASHRAE 52.2 from the American Society of Health, Refrigerating and Air Conditioning Engineers
  • ISO 16890 from the International Organization for Standardization

Both of these standards provide methods for evaluating and classifying different filters for use in general ventilation and dust collection systems. Although the two standards are similar, they evaluate filter performance differently: ASHRAE 52.2 measures the number of particles a filter can remove, while ISO 16890 compares the mass of particles before and after they pass through the filter.

How ASHRAE 52.2 Standard Works

The ASHRAE 52.2 standard includes procedures for testing a filter’s efficiency in removing airborne particles ranging from 0.3 to 10 micrometers. This standard uses a scale called the Minimum Efficiency Reporting Value (MERV), which rates a filter's ability to capture particles on a scale of 1 to 16. A higher MERV rating signifies better filtration performance.

The MERV ratings serve as a useful tool for those involved in planning and operation of dust collection systems. It helps plant engineers and operators of dust collection systems assess filter efficiency across different particle sizes, and choose the most efficient filter for specific contaminants as shown by the chart below.

For instance, in a bill processing facility, an operator might choose a filter that is highly efficient at capturing paper dust particles of a specific size that is generated during the manufacturing. If the task is to remove welding smoke, a better choice would be a filter optimized for much smaller size particles. Commercial filters, such as cartridges, V-cells, and rigid cells, typically have MERV ratings of 14 or higher. The highest filtration efficiency comes from HEPA filters rated MERV 17, which are ideal for locations with hazardous biological contaminants. However, using a filter with a higher MERV rating than necessary can actually hinder performance.

It's important to note that MERV ratings reflect the efficiency of new filters and their initial performance under static conditions. They do not predict how a filter will perform over time. As dust collectors and filters handle emissions in dynamic systems, their efficiency will fluctuate. Factors such as differing dust types and loads, along with regular filter cleaning, affect filter efficiency in ways not accounted for by MERV ratings. Furthermore, MERV ratings do not consider changes in energy use throughout the filter's lifespan.

ISO 16890 Filter Rating Approach

The ISO 16890 standard was created to establish a uniform protocol for testing and classifying filters, fostering greater consistency across the air filtration industry and facilitating international trade. The International Organization for Standardization promotes it as a novel and more effective classification system compared to previous standards.

ISO 16890's approach to testing and rating filters is different from that of the ASHRAE 52.2 standard. ISO 16890 evaluates filters based on their ability to capture particulate matter (PM) ranging from 0.3 to 10 micrometers. It tests both a new, unconditioned filter and a used, conditioned one for particle removal efficiency. The average filter efficiency for each size range is then determined by calculating the mean of the initial and conditioned efficiencies.

The most harmful and smallest particles are classified in the following PM ratings (See Chart 2 for a more detailed outline of these classifications):

  • PM1 (0.3 – 1.0 um)
  • 5 (0.3- 2.5 um)
  • PM10 (0.3 – 10 um)

The ratings show a direct correlation between air pollution and health.  For example, the ears, nose, and mouth can filter coarse particles of 10 microns. The throat can filter particles less than 10 microns, and the lungs can filter those less than 2.5 microns.  The most harmful particulates in the PM1 category include combustion particles like diesel fumes, bacteria, and viruses. These particles can penetrate the lungs and enter the bloodstream, potentially leading to health complications. ISO 16890 classifies the efficiency of filters based on their ability to remove contaminants of a certain mass. This chart is a visual reference.

While the ePM (from ISO 16890) and MERV (from ASHRAE 52.2) ratings come from distinct testing approaches, they both utilize a 12-channel analyzer to measure the concentration of particles within the same size ranges, from 0.3 to 10 micrometers. Both methods compare the concentration of particles before and after passing through the filter. The chart below offers a rough comparison between these two methods of evaluating filter efficiency.

ISO 16890 Controversy

The Air Conditioning, Heating and Refrigeration Institute recommends maintaining the ASHRAE 52.2 standards, as it allows the United States to uphold control over suitable testing methods. Given that HVAC systems in the U.S. differ from those in Europe, substituting another standard for ASHRAE 52.2 could cause significant industry expense and disruption.

Conversely, Camfil APC, a global leader in the air filter industry, endorses ISO 16890. This standard offers enhancements over EN779:2012 by providing test procedures that more accurately reflect real-world filter performance. It also categorizes filter performance against three different particle sizes. Manufacturers concerned with PM emissions might find the ISO 16890 reporting values beneficial.

The ongoing question is whether one standard will eventually replace the other, as the U.S. currently favors ASHRAE 52.2, while Europe follows ISO 16890. Manufacturers who trade abroad may find that their customers require testing reports based on ISO 16890, not just a comparison chart to MERV ratings. Therefore, even if your business doesn't operate abroad, it's important to be familiar with ISO 16890.

Closing Thoughts

The quality of indoor air can be negatively affected by various factors, including temperature, humidity, mold, recycled air, manufacturing dust, construction materials, and airborne chemicals. Dust collection systems with efficient air filters mitigate poor IAQ. Filter efficiency can be evaluated using two industry standards: ASHRAE 52.2 and ISO 16890. Only time will tell which standard will be universally adopted.

Camfil APC offers a full line of air filters to improve indoor air quality in a variety of manufacturing settings.  Contact an air filter expert to find the best solution for your application or learn more about MERV ratings and ISO 16890 standards. For more information about Camfil, visit us here.