A Dust Mask And Respirator Primer

Farm work can often involve exposure to dust, mold spores, pesticides, solvents, and toxic animal gases. You or your employees may also have to work in oxygen-deficient grain stores, silos, and enclosed manure pits that can be extremely dangerous without a proper respirator. In order to stay safe, you must choose respiratory equipment for specific tasks—in some cases, your life can depend on it. While some dust masks and respirators come one-size-fits all, masks and respirators are made in various models to suit different contaminants. Knowing which mask is appropriate for a specific task is essential to protecting your lungs. To know which mask is the right one, requires knowing what contaminants you will be exposed to.

Respiratory Hazards Requiring A Dust Mask or Respirator

Farmer's Lung and Organic Dust Toxicity Syndrome (ODTS) are reactions to dust from moldy hay or grain and may result in costly medical treatment, permanent lung damage, or even death. It’s worth realizing that in many cases, a five or twenty-five dollar respirator could have prevented nagging and even permanent lung damage from long-term exposure to common contaminants.

Respiratory hazards can be broken into three distinct groups:

  • particulate contaminants
  • gases and vapors
  • oxygen deficient atmospheres

Particulate Contaminants

Typically considered dust, fumes, and mists, particulate contaminants are not always visible. While everyone knows what dust looks like, not all dust is visible. Mold spores—often present in hay—are microscopic. Mists, on the other hand, are liquid droplets in suspension, usually found near mixing, spraying, and cleaning operations. Fumes are solid particles of evaporated metal, also microscopic, which are formed during activities such as welding. If, like many farmers, you do your own welding, it’s important to know this fairly common repair procedure also produces contaminants harmful to respiration and not just a piercing, bright light.

Gases And Vapors

Gases are chemicals that are invisible and can be odorless at room temperature. Most of us are taught the dangers of carbon monoxide poisoning—don’t run the car in the garage, etc. and in recent years we have become more aware of its dangers in the house. We now have indoor carbon monoxide alarms. But the gases produced in manure pits (hydrogen sulfide) and conventional silos (nitrogen dioxide) are equally dangerous and should be treated with the same respect that you do carbon monoxide.

Vapors are toxic contaminants released from liquids like paint and lacquers, glues and pesticides.

Oxygen Deficient Atmospheres

To breathe normally, the air around you needs to contain an oxygen content of about 21%. However, the oxygen levels in sealed silos and some manure storage units can be as low as 5% due to the gases created in these environments (hydrogen sulfide and nitrogen dioxide) that essentially displace oxygen.

The Nuisance Dust Mask

Widely recognizable, the nuisance dust mask most often comes with a single elastic strap and is constructed from thin, white filter paper. The nuisance mask looks like a Disposable Particulate Respirator which utilizes two straps and provides more protection, as described below. One-size-fits-all, the nuisance dust mask is good for light duty work—sweeping garage/shed floors etc.—by people with no history of respiratory illness.


There is no respirator made to handle every situation. Instead, respirators are constructed for specific purposes. An “approved” respirator is a respirator approved by the National Institute for Occupational Safety and Health (NIOSH). Older NIOSH approved respirators or filters have a number preceded by the letters “TC”. Newer models have the NIOSH TC approval number followed by a description—for example, ”NIOSH TC 23C dual cartridge half mask with disposable filter used for pesticides and ammonia.”

Recently manufactured respirators are rated for filter-efficiency, as well, in reducing dust, mists, and fumes; as well as their duration against oil-based chemicals or pesticides. They include the following designations:

  • N—Not resistant to airborne oils, will plug quickly
  • R—Resistant to airborne oils for up to 8 hours
  • P—Oil proof and possibly resistant to airborne oils for up to 8 hours—change the filter after every 40 hours of use or after 30 days—whichever comes first

The filter efficiency rating and resistance to oils rating can be found in several locations: on the respirator unit, pre-filters, cartridges, packaging, and in advertisements. If you can’t find rating information, approved respirators will also have at least two elastic straps or a headband.

Respirator Categories

Respirators come in two categories: air-purifying and supplied-air. Air-purifying respirators are made in a variety of forms for a variety of different tasks. These respirators include filters through which the wearer breathes. These respirators do not supply oxygen and should not be used in oxygen-deficient areas, like sealed silos, or in toxic areas, like manure pits. Air-purifying respirators are excellent for work in hay barns, when working dry soil or applying pesticides, or for general construction work, particularly if you are working around sawdust or fiberglass dust. These respirators are generally known as “negative pressure” respirators because the wearer pulls oxygen through the mask, thus filtering the air. It is important to note that these respirators do not supply oxygen. In fact, they make the user work a little harder to get normal oxygen levels. If you are asthmatic or have lung or cardiovascular disease, make sure to ask your doctor if it is safe for you to use a respirator.

Air-Purifying Respirators

Disposable Particulate Respirators

Disposable particulate respirators look very similar to the standard nuisance dust mask but they have two straps. The disposable particulate respirator is an approved respirator that will protect you from particulate contaminants like dusts, mists, and some fumes. The filters trap the particles you would otherwise breathe. These are great for general “dusty” work, like haying, tilling, fertilizing, working with grain, and sweeping.

These masks come in reusable and disposable forms. They should be replaced when breathing becomes too hard. At that point the filter is saturated. If the fit is not correct or changes, you may end up smelling or tasting the substance you’re working around—another sign it’s time to get a new disposable particulate respirator.

Chemical Cartridge Respirators

Chemical cartridge respirators are made to filter low levels of toxic gases and vapors by use of an absorbent material, such as activated charcoal. This form of mask can also be outfitted with particulate filters, so this mask is great for work that will expose you to gases, vapors, and the particulate contaminants disposable particulate respirators are designed to handle.

Chemical cartridge respirators come in full and half-mask versions. The full-face model offers eye and face protection. Half-mask models are available in disposable and reusable versions. Full-face models offer the best protection, of course, and will seal well to your face. The filter cartridges screw into the mask and are changeable. Make sure to follow the manufacturer’s recommendations, but typically you can get eight hours of use from a cartridge.

When you begin to taste or smell the contaminant you’re working around, or if you begin to feel dizzy, immediately change your cartridge. These masks should not be used in areas that are life-threatening.

Fitting, Testing, And Maintaining Your Respirator

Respirators come in all sizes and shapes. It’s smart to try on the one you need first, before buying. The key to a good fit is the seal around the face. Cover the exhale port with your palm and breathe out. The mast should slightly push from your face. Then cover the inhale ports and inhale. Hold your breath for 10 seconds. The respirator should suck onto your face and remain that way for the whole 10 seconds. If your seal isn’t perfect, try re-adjusting the straps, reposition the respirator, and repeat the tests. The seal is what will keep you alive. If, when using, you can smell or taste the contaminant, or if you become dizzy or nauseous, leave the area immediately and move into fresh air.

If you chew gum or tobacco or if you have facial hair or stubble—these can alter the seal of your respirator. If you wear glasses, you can get adaptors for securing lenses inside the face-piece of a full-face respirator. Contacts should be avoided as contaminants can stick to them and cause eye damage.

Inspect your respirator before each use. Accumulated dirt around the face-piece, detergent residue, cracked or missing valve covers, a cracked face-piece, cracked or missing head straps should be dealt with before use. Never try to perform more than a basic, approved part replacement such as filters or head-straps. Do not try to substitute parts from other respirators for your respirator. If you need more information, call the manufacturer.

You can clean your respirator with warm water and soap after removing all cartridges and filters. After a complete drying, store the respirator in a sealed bag. If you leave cartridges and filters attached, they can collect contaminants from the air and become saturated. Duct taping the cartridge face works great for preventing non-use environmental exposure.

It all begins with understanding the contaminant and risk you are dealing with. Once you are certain about environmental risks, you can select the right respirator for the job. Your life can literally depend on it.

Do you have important information we didn’t include? Tell us in the comments section!