Choosing respiratory protection equipment is an important process that involves many factors, says Jeffrey Birkner.
The most obvious factor is the type of hazard — this drives whether or not a chemical cartridge must be used, a particulate filter, a combination of both, or a higher level of protection.
The concentration of the contaminant will drive whether a half-mask, full-face, or higher level of protection is needed. Full-face respirators must also be considered when eye protection is required to protect from things such as irritants, or skin and mucosa absorption.
Other factors include the chemical resistance of the materials in the respirator, temperature of the environment in which the respirator is to be used, and how the respirator will be cleaned and serviced.
Vision, frequency and duration of use, and fit are also important considerations. All of these, as well as other programme elements, must be incorporated into the written comprehensive respiratory protection programme.
One factor which is often overlooked is comfort – a respirator that is not comfortable is less likely to be worn. Comfort is affected by material selection, visibility, weight and ease of use as well as breathability. Duration and frequency of use must also be considered when evaluating the comfort factor.
Disregarding the employees’ input in selecting a comfortable respirator simply increases the likelihood of non-compliance with the respiratory protection programme and the likelihood that exposure will occur.
Factors that directly impact respirator comfort include: material, vision, weight, amount of dead space, the type of strap or harness and its ability to be properly adjusted, and overall resistance, or breathability, of the respirator.
Different types of materials feel different to the skin. When a respirator is in contact with the skin for extended periods of time, the material’s feeling and softness are important factors.
Today, there are a multitude of materials from which respirators are made. Sometimes choice is dependent upon the chemical contaminant and the respirator’s resistance to the substance.
Once the correct materials are chosen, it is important to involve the actual users to see which respirators are more comfortable.
Vision is obviously a safety issue but it’s also a comfort issue – the greater the field of vision the more comfortable he/she is and the less apprehensive about wearing the device.
Lack of proper direct and peripheral vision tends to make people uncomfortable and will usually impede their ability to work efficiently. The less vision that they have the more they must rely on their other senses to detect and perceive signals, including hazards in their work environment.
Weight is important – the heavier a respirator the greater the user fatigue. Although a few ounces difference may seem insignificant in the short term, it significantly adds to the fatigue factor when a respirator is worn for extended periods of time.
Dead space is the amount of air that is found between the face piece and the user’s face – the less dead space the more comfortable the user. Dead space also contains residual amounts of exhaled carbon dioxide that affects circulation and breathing and can cause headaches and drowsiness – the greater the dead space, the greater the carbon dioxide load.
The dead space displaces oxygen in the face piece so the user must breathe deeper to obtain the requisite amount of oxygen. Additionally, excess carbon dioxide levels can cause a claustrophobic feeling.
In addition to the materials used in a respirator’s straps and harness, how well the straps hold the respirator in place and the design of the strap both affect overall comfort. For instance, thinner straps tend to exert more force on the skin. Whether or not straps pull on hair and their overall tension adjustability also affect comfort significantly.
Finally, there is resistance or breathability – the easier it is to inhale and exhale the less fatigue created over an extended period of time. In fact, one study showed that increased inhalation resistance was associated with decreased work performance.
The US’s National Institute for Occupational Safety and Health (NIOSH) requires that respirators meet inhalation and exhalation resistance criteria, but only sets a maximum. The lower the resistance, the better off the employee and more likely that he/she will be willing to wear the respirator when required. Increased resistance can make the employee feel out of breath and claustrophobic.
Once the basic questions have been answered and the type of respirator chosen, the employer should obtain several designs and then have the employees try on the respirators to see which one they prefer. Having employee “buy-in” to the respirator programme is critical and should never be overlooked.
Jeffrey Birkner, PhD, is vice president, Technical Services, of Moldex-Metric, Inc., which specialises in hearing and respiratory protection for industrial worker safety.