This or That?

By Joe O'Connor | Oct 15, 2007




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What do you do when the air quality at work is found to be a hazard? The best way to protect your employees is to get rid of the hazard. Ventilation is an engineering control that may eliminate respiratory hazards. You can try to control exposure administratively through scheduling. Work may be able to be done when contaminants are not present in harmful quantities. As a final precaution, respirators are a viable solution, but it is critical to select the correct respirator.

The first step is to perform an exposure assessment, which reveals the identity and nature of the hazard as well as the expected level of exposure. The Material Safety Data Sheet (MSDS) is a great resource for this evaluation. It provides details on the substance and supplies recommended or required occupational exposure levels. Once the substance is identified, you can determine the levels present by sampling. This requires a worker to wear monitoring devices to collect the contaminants present. The worker must be protected from the worst possible exposure during sampling.

An alternate method of determining the level of exposure is to use “objective data” assessments, which rely on estimates. One procedure is to estimate the amount of contaminant released in a room based on the substance’s physical and chemical properties, room dimensions, air exchange rates, etc. The other estimate uses data collected from others performing the same type of work under similar conditions. Industry-wide surveys may be available from trade associations or studies performed by other safety organizations. When using this data, allow for variation. Look at worst-case scenarios, and ensure a safety factor is included in your estimates.

Depending on the identity and nature of the material in question, you can determine if an air-purifying or air-supplying respirator is needed. Air-purifying respirators use filters, cartridges or canisters to clean air by passing air through the filtering device to remove the contaminants. Air-supplying respirators provide clean air to the user from a source other than the air around the user. Air-supplying respirators must be used when there is a lack of oxygen.

Three commonly used air-purifying respirators exist. Particulate respirators remove particles such as dust, mist and fumes, but do not work for gases and vapors. Gas and vapor respirators use a chemical cartridge or canister to remove the dangerous substance from the air. The cartridge or canister used is specific to a given gas or vapor. Combination respirators should be used in situations that contain both harmful particulates and a dangerous gas or vapor.

Air-supplied respirators deliver clean air through a hose from a fixed source. The source may be a tank or clean air pumped along the hose from an area outside the work zone. A self-contained breathing apparatus allows the worker to carry the clean air in a wearable, clean-air supply pack. Air-supplied respirators usually are used in areas where the air is not immediately dangerous to life and health.

In addition to matching the type of respirator to the contaminant, each respirator has a predetermined assigned protection factor (APF). The APF must be matched with the level of exposure the employee will experience. It is the expected workplace performance of a respirator. The APF supposedly reduces the level of the hazardous substance in the workplace.

If the level of a substance in the air was 50 parts per million (ppm), it is assumed a respirator with an APF of 10 will reduce this level to 5 ppm (50/10). This is then compared with the exposure limit set by the Occupational Safety and Health Administration (OSHA) to ensure the respirator provides adequate protection.

Other factors that will influence the respirator chosen include the following:

  • Physical layout of the site—For example, at a site where space is limited, a self-
    contained breathing apparatus may not be the best choice. Also, if a worker moves machinery or something that could snag a hose, air-line respirators would not be a good fit.

  • Worker’s medical condition—Wearing a respirator increases physical stress more than doing the task without added equipment. A medical evaluation of the worker is necessary, and it may prohibit the worker from wearing a respirator or identify limitations on the type of respirator that can be used. A worker who may have problems with restrictive breathing conditions could not wear a negative-pressure respirator.

  • Worker comfort—If the equipment is not comfortable, it won’t be used. Respirators vary in weight, skin comfort, ease in breathing and in-mask temperature and humidity. These should be considered when making the final decision.

Respirators are crucial pieces of personal protective equipment that are necessary to complete many jobs, but always remember, no one should use a respirator who has not been medically cleared or if they are not trained to use it. Misusing a respirator can be as dangerous as not using one when it is needed.  EC

O’CONNOR is with Intec, a safety consulting, training and publishing firm that offers on-site assistance and produces manuals, training videos and software for contractors. Based in Waverly, Pa., he can be reached at 607.624.7159 or [email protected]. KELLY is a safety and health specialist with Intec.


About The Author

Joe O'Connor is with Intec, a safety consulting, training and publishing firm that offers on-site assistance and produces manuals, training videos and software for contractors. Based in Waverly, Pa., he can be reached at 607.624.7159 or [email protected].


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