I'm frequently asked this question and it seems that there are hundreds of answers demonstrating the importance of respirator fit testing, but here's another reason. Recently I conducted fit testing to a new full facepiece respirator. After donning and obtaining information regarding comfort and fit, the wearer conducted positive and negative pressure user seal checks. As an experienced fit tester I was satisfied that the respirator was properly positioned and visually appeared to fit very well. The respirator wearer passed both user seal checks and I too was satisfied with the results. A comfort assessment period was conducted prior to the start of quantitative fit testing, as required by OSHA. The fit test was started after the comfort assessment period and to my surprise the resulting fit factor was 11 (ie, significant leakage). This was surprising since the respirator was brand new and appeared to fit very well. I reexamined the positioning of the facepiece and recognized the head straps were loose. I instructed the subject to readjust the headgear, repeated user seal checks, and conducted another comfort assessment period before starting the fit test. To my surprise, the respirator failed the fit test. Once again I evaluated the respirator and the straps were visibly loose. The entire process was repeated a third time, with the same results. Inspection of the respirator identified that the serrated edges on the head gear were missing, consequently, the retaining buckle would not maintain adequate strap tension. The missing serrated edges were surprising, since this was a new facepiece. Obviously, this problem represented a manufacturing defect. At the time of this writing, I am in the process of contacting the manufacturer and NIOSH. Results will be shared in a future newsletter. Some important conclusions are:
Another reason why we conduct fit testing:
A recent study examined the direct and indirect cost of chronic obstructive pulmonary disease (COPD) and asthma. The authors found that $6.6 billion was spent in 1996. The study also estimated that there were approximately 15,000 occupational COPD deaths and approximately 800 occupational asthma deaths in 1996. These numbers far exceed the more recognizable occupational lung diseases such as coal worker's pneumoconiosis, asbestosis, and mesothelioma. The study which was recently reported in the journal CHEST concluded that due to the rising costs associated with COPD and asthma, preventive measures are important. Obviously, reducing exposures to acceptable (ie, safe) levels with appropriate engineering controls is the desired solution. When these controls are not feasible or possible, a properly used and fitted respirator will help. Let's thank the authors; J. Paul Leigh, et al. for their work. Source: Chest 2002; 121:264-272.
Sweetener fit testing is not designed to detect all size and shape leaks!
A recent 3M Job Highlights newsletter (page, 13, volume 19, #2, 2001) summarized the 2001 AIHce presentations given in New Orleans. One of the presentations represented the thesis work of Mike Hodges a graduate student in Dr. McKay's fit test laboratory. Since Mike was unavailable to speak at the 2001 conference, the presentation was given by Dr. McKay. Results from this study demonstrated that qualitative fit testing with sodium saccharin did not have adequate sensitivity to detect leakage through exhalation valves. While 3M and I have different opinions and apparently different conclusions from this study, I was surprised at their written explanation. They state: "Because the leaks introduced into the exhalation valve require abrupt directional changes, they bear no resemblance to faceseal leaks on respirator wearers. It is well known that abrupt changes cause aerosol particles to be removed from the airstream by inertial impaction. For this reason, while saccharin has been shown to be an effective qualitative fit test, it is not intended to detect the size and shape of the leak used in this study." Our responses are that these leaks represent problems we've experienced during fit testing with client facepieces. Thus, they represent real leaks. In addition, I can't imagine a more direct path for a potential contaminant to enter a facepiece than through the exhalation valve. Lastly, 3M basically states that the saccharin fit test (ie, sweetener) is not designed to identify leakage through damaged facepieces, rather it is intended to identify faceseal leakage only. This suggests that saccharin qualitative fit testing (ie, sweetener) is not necessarily expected to identify damaged facepieces during repeat (ie, follow-up) fit testing. We believe one purpose of fit testing should be the ability to detect damaged facepieces in addition to faceseal leakage. This is one reason why we encourage fit testing respirator user's in their own facepiece.
Full Facepiece Fit Test Reminder:
Remember that the current OSHA respirator standard (1910.134) does not permit qualitative fit testing for full face negative pressure respirators, in areas where they are required to be worn. Examples of qualitative fit test methods are: Sodium Saccharin (sweetener), Bitrex (bitter agent), Isoamyl acetate (banana oil), and irritant smoke. Qualitative fit testing is only permitted for fit testing tight fitting facepieces that are allowed to pass with a minimum fit factor of 100. Since OSHA requires a minimum fit factor of 500 (and ANSI requires a minimum of 1,000), qualitative fit testing of negative pressure full facepiece respirators is not permitted when this style is required to be worn.
New Standards for Smoke Hoods Coming:
Smoke hoods are designed to provide approximately 15 minutes of air purifying capabilities when used in building related fires. The toxicity of fires is both complex and variable, however, respirator manufacturers are responding with new products to meet this need. Research has shown that many fire related deaths are not due to the fire itself, rather the toxic components of smoke inhalation. If a convenient, air purifying smoke hood was available, the additional time provided may improve escape capabilities. The new smoke hoods under development are designed to provide approximately 15 minutes of escape from a fire, provided, adequate oxygen is available. These devices are not appropriate or intended for first responders. Government standards for these devices do not currently exist, however, the International Safety Equipment Association (ISEA) is developing a standard that is intended to provide design guidance to manufacturers. Standards are important because it will help consumers identify and select an escape device that meets a minimum set of criteria. Currently the draft standard is designated ANSI/ISEA 110-200x. We'll keep you notified of the status of smoke hoods as new information becomes available.
Irritant smoke fit test results presented at 2002 AIHce:
Congratulations to Erin Snyder, a former graduate student of Dr. McKay's laboratory and now an NIOSH employee. Erin presented the results of her thesis work at the 2002 AIHce in San Diego. This work was conducted at the University of Cincinnati. Her studies showed that irritant smoke did not have adequate sensitivity to detect fit factors less than 100. Her studies also demonstrated that those subjects who did respond to the smoke (ie, cough reflex), required more than 3 minutes on average to detect the irritant. This means that a transient leak, would not necessarily be detected by irritant smoke fit testing, even among those subjects who were able to detect the smoke. Details of her abstract are available on the AIHA web page at www.AIHA.org.
Qualifications for persons who conduct fit testing:
Readers are reminded that ANSI Z88.10-2001 (Respirator Fit Test Methods) outlines the recommended training requirements for persons who conduct respirator fit testing. While ANSI and OSHA don't require formal certification, both organizations recognize the benefits of formal training programs. In general, the fit test operator should be familiar with Z88.10 and OSHA fit testing guidelines. The fit tester should also be familiar with the types of respirator facepieces used in the workplace and should certainly be thoroughly familiar with respirator inspection procedures. With regard to the fit test method used, the operator should understand the limitations of the equipment and know how to set-up, prepare, and calibrate the equipment. The ability to recognize erroneous results and their causes is critically important. The fit test operator must observe the subject during the donning procedure, while conducting user seal checks, as well as throughout the fit test itself. The fit test is also a perfect opportunity for the operator to provide the respirator wearer additional training on his/her respirator. Copies of ANSI Z88-10-2001 are available from the AIHA web site at: www.AIHA.org
Respirator Training
The University of Cincinnati is pleased to announce the following courses Respiratory Protection and Fit Testing courses that may be of interest to you or your staff. They are1. Overview of Respiratory Protection (1 day, on September 16, 2002), and2. Respirator Fit Testing Workshop (2 days, on September 17 & 18, 2002).Programs are held near the Cincinnati airport.
Information regarding these courses is available by contacting www.DrMcKay.com or 513/475-7712 and ask for Jeff. Alternatively, you can speak with Anita at 513/475-7713 in the afternoon.
These courses are an excellent way to obtain up to date information and clarification of respiratory protection issues. Individuals who intend to take the fit testing workshop, but have little or no experience with respiratory protection should take the one day overview class in addition to the 2-day fit testing workshop. The fit testing workshop provides an opportunity to see and experience all types of fit test methods (qualitative and quantitative). This hands on workshop provides extensive hands-on fit test training in a small group atmosphere.
Dr. McKay is a member of the ANSI Z88 Respiratory Protection Committee, the Z88.10 Fit Testing committee, the AIHA Respiratory Protection committee, and others.
Thank you for your continuing support and hope to see you at a future training course.
Roy McKay, Ph.D.
Course Director
University of Cincinnati
www.DrMcKay.com