In Techniques

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2020 has many of us spending more time than ever in the workshop. Whether it’s sketching out your newest build or taking the next steps towards finishing a piece, all that extra time in your shop may have you considering making changes to your space. No matter the size of your shop, improving your dust collection system can be one of the most worthwhile investments for any woodworker. A cleaner shop is not only healthier for your lungs but healthier for your equipment too. Best of all, your dust collection plans don’t have to break the bank. Whatever your budget may be, there is always something you can do better to enhance air quality in your shop.

Why Wood Dust Is Harmful

The foundation of good dust collection practices starts with understanding why it’s necessary in the first place. Every woodworker should be aware of the known health risks associated with the byproduct of their activities—wood dust. Frequent exposure to wood dust can irritate the skin, eyes, and respiratory tract, leading to rashes, asthma, or loss of respiratory function. Of gravest concern is the strong and consistent association many studies have found between exposure to wood dust and cancer of the nasal cavity.[1]

Wood dust is known to be a human carcinogen. In its Report on Carcinogens, the National Toxicology Program, a division of the U.S. Department of Health and Human Services, lists wood dust among the substances known to cause cancer in humans.[1]

And it’s the finer dust particles—those 10 microns and smaller—that are the most hazardous. To put that size in perspective, consider that a human hair is about 100 microns thick, while airborne dust particles smaller than 20 microns are invisible to the naked eye.

The trouble starts when your respiratory system must deal with large amounts of respirable dust (below 10 microns in size). Heavy exposure to this dust can overwhelm the lung’s natural defenses and lead to inflammation and swelling of the airways, which cause symptoms such as shortness of breath, increased sputum and coughing, nose bleeds, sinus trouble, or bronchitis. It can also provoke an asthma attack or, in the case of western red cedar, cause asthma as an allergic reaction

Over the last 50 years there have been many case studies of woodworkers who have reported cancer of the sinonasal cavities and paranasal sinuses, such as adenocarcinoma. Several studies have identified oak, beech, birch, mahogany, and walnut as the species of wood most often used by patients.[2]

Reducing Exposure – What You Can Do

There are a lot of misconceptions about what is or isn’t considered effective dust collection amongst the woodworking community. Regardless of the method used, the primary purpose of dust collection is to limit exposure to wood dust. Keeping this fundamental principle in mind, here are some ways you can achieve this goal in your workshop.

Wear A Respirator

A respirator is the simplest and often the most economical addition to your shop safety gear. Ideally you want one that is approved by the National Institute of Occupational Safety and Health (NIOSH), which will filter 95% or more of airborne particles, depending on the filter’s class (N95, R99, P100, etc.). The numbers in a filter’s class (95, 99, or 100) correspond to the level of filtration of airborne particles (at least 95%, 99%, or 99.97%), while the letters N, R, and P refer to the filter’s oil resistance (N for not resistant, R for somewhat resistant, and P for strongly resistant). HE (High Efficiency Particulate Air) is the only class without a number—filtering at least 99.97% of airborne particles when used with a powered air-purifying respirator. To confirm you are using a respirator approved by NIOSH (yes, counterfeits exist), check the respirator itself or its accompanying packaging for a number starting with “TC”; this is an approval number required by NIOSH for all NIOSH approved respirators.[3]

Collect Dust at the Source

OSHA recommends installing collectors at the point where dust is produced, such as the dust port of the woodworking machine.[4] You must position the suction hood as close as possible to the source of emission—your lathe, grinder, or other woodworking machinery. It’s crucial that dust be picked up as it’s generated and then directed into the collector. If you lose the dust to your shop air, the task of collecting it becomes futile. You will be inhaling that dust and sweeping it from your machines and floor.

Maintain Sufficient Air Volume/CFM

You can determine the efficiency of dust capture fairly accurately by a quick visual inspection of your machinery. Inadequate air volume/CFM allows dust from your grinder to escape onto the floor and into the air. Ensuring your ducting is large enough in diameter and efficiently laid out are two ways you can minimize restrictions on airflow.

Most woodworking equipment requires about 250-1000 CFM. The amount of CFM needed will vary depending on the size and number of woodworking tools running simultaneously. Most average size table saws, planers, and jointers with 2-5 inch diameter ports need approximately 300-600 CFM to clean well (Table: Airflow vs. Pipe Diameter). A machine that loses a lot of chips or is emitting a visible plume of fine dust needs more airflow.

Use a High-Quality Filter

The final stage in dust collection is filtering the fine dust. It doesn’t make sense to go through all the trouble of collecting the dust if you still allow the finest dust to pass through the filter and out into the shop air. The smallest dust is the most unhealthy to breathe and when it becomes airborne, inhalation is inevitable.

Effective filtration requires quality filter media of sufficient quantity/surface area. You want to filter near 100%, down to the smallest particle (10 microns or less in diameter) –what industrial hygienists refer to as the PM10 range.

Filter media certified to a certain standard, such as HEPA (tested to be 99.97% efficient at 0.3 microns) is also a must.

Before purchasing a dust collector, there are a few questions you should ask about its filtration.

  • What type of filter is supplied?
  • What is its efficiency rating?
  • Can a specification sheet be provided?
  • Has the filter media been tested by an approved third-party agency?

Don’t let dust collection be an afterthought. Follow these fundamentals to ensure a safer, healthier, and more enjoyable workshop environment.

 

Further Reading and Sources

For a more comprehensive source on CFM exhaust volumes, check out Industrial Ventilation: A Manual of Recommended Practice for Design by the American Conference of Governmental Industrial Hygienists.

[1] National Toxicology Program. 2016. Report on Carcinogens, 14th Ed.; Research Triangle Park, NC: U.S. Department of Health and Human Services. https://ntp.niehs.nih.gov/go/roc14.

[2] International Agency for Research on Cancer. 1995. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, No. 62; Wood Dust and Formaldehyde. https://www.ncbi.nlm.nih.gov/books/NBK493444/.

[3] National Institute of Occupational Safety and Health (NIOSH), National Personal Protective Technology Laboratory. Section 1: NIOSH-Approved Respirators. Centers for Disease Control. https://www.cdc.gov/niosh/npptl/topics/respirators/disp_part/respsource1quest2.html.

[4] Occupational Safety & Health Administration (OSHA). Wood Dust: Possible Solutions. U.S. Department of Labor. https://www.osha.gov/SLTC/wooddust/solutions.html.


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