FAQ: How do I select the most efficient filter media for my dust collector?

The first thing to consider is the maximum allowable emissions for the type of dust to be filtered. OSHA sets the standards for indoor air quality, and the EPA controls limits on air exhausted outside. Toxic materials such as pesticides and herbicides, potent pharmaceutical compounds, hex chrome, cadmium, and lead have very low emission limits and almost always require HEPA after filters downstream of the dust collector. The more efficient the dust collector, the less often change-out of the HEPA filters will be required. Exposure to the dust during change-out of both the primary and HEPA filters may require bag-in/bag-out containment features.

Even with less toxic dusts like paper, it makes no sense to return the air from the collector to the work space unless the air is at least as clean as the Permissible Exposure Limits (PELs). A typical PEL for paper dust is 5 mg/m³ or .002 grains/cu ft. Using media that the manufacturer will only guarantee at a higher level than the PEL could put you out of compliance with OSHA. Returning the air can save huge amounts in heating and cooling costs. Many dusts can be explosive, so remember to follow all National Fire Protection Association (NFPA) guidelines when returning any air into the plant.

Finally, some media may have higher pressure drops that can add to fan horsepower, leading to higher energy costs. Along with the higher pressure drops, the cleaning system may require more compressed air to maintain a stable pressure drop across the filters. How the cartridge is designed and pleated can help lower or eliminate the added pressure drop and reduce total energy needed to run the dust collector. Wider, evenly spaced pleats can allow the air to move through the filter without the added pressure drop and also allow the dust to be easily pulsed out.

For more related information, read the Media Types section of the article, Trends in Pleated Cartridges Filters. The full article begins here and can be downloaded as a PDF file.