Editor’s note: This article introduces recently revised performance terms for respiratory protection. The revision was a project of the AIHA Respiratory Protection Committee. A complete list of new and revised definitions follows this article.

Health and safety practitioners, program administrators, and users of respiratory protection are likely familiar with the term “protection factor,” which has been in common use since the mid-1970s. The term was originally intended to express the level of protection a given type of respirator would provide when worn. Mathematically, the protection factor was expressed as the ratio of challenge agent outside a respirator (Co) to that which would penetrate into the wearer’s breathing zone (Ci). The “original” protection factors used in the United States were based on quantitative fit-testing studies performed at Los Alamos National Laboratory (formerly Los Alamos Scientific Laboratory).

In the early 1980s it was recognized that respirator performance is a function of where and how the measurements are made. For example, Co and Ci measurements made in workplaces using integrated sampling methods were found to differ from measurements made on the same type of respirator in laboratories with quantitative fit-testing systems, as explained in a 1986 paper published in the Journal of the International Society for Respiratory Protection. Furthermore, researchers sometimes controlled one or more of the factors that affected respirator performance to better understand and characterize the influence of each factor. Thoughtful discussions began in the AIHA Journal and eventually became a project for AIHA’s Respiratory Protection Committee. The terms in use today—quantitative fit factor, workplace protection factor, assigned protection factor, and so on—were formalized by the Respiratory Protection Committee and published in the AIHA Journal in 1985. The committee later revised the terms for clarity and republished them in 2002. The latest revision was undertaken to clarify and refine minor issues, account for new measurement technology, and add terms for research that did not fit neatly into any of the previous terms. Three new terms were added to define laboratory performance measurements conducted with respirators mounted to manikins. The revised and newly added terms are intended to expand and clarify the meaning of measurements made under a wider variety of conditions. The terms are applicable to all respirator types. They are appropriate regardless of the instruments or analytical methods used for the measurements, and are unaffected by statistical analysis or other mathematical treatment. In general, the performance terms have no legal standing, but several of them have been incorporated into OSHA regulations, NIOSH publications, and ANSI standards. Researchers are strongly urged to properly use these terms in their publications. These terms are necessary to properly depict where, how, and under what circumstances respirator performance is measured or described. As noted earlier, it has long been known that fit measurements (now called quantitative fit factor, QNFF) differ from protection measurements (now designated workplace protection factor, WPF). The same limitation should be applied to every term: each is discrete, and no measurement has been shown to accurately predict another. While the original term “protection factor” has served our profession well, it lacks the precision to describe all scenarios in which respirator performance is discussed. It should not be used without the proper modifier as described in these definitions. LARRY JANSSEN, CIH, is an industrial hygiene consultant in Stillwater, Minn. He can be reached at (651) 430-0815 or lljanssen@centurylink.net.
 ROY MCKAY, PHD, is director of Occupational Pulmonary Services at the University of Cincinnati in Ohio. He can be reached at (513) 558-1234, ext. 88 or roy@drmckay.com. Authors’ note: Reader feedback is welcome. Comments can be directed to the authors or to Jessica Hauge, chair of the Respiratory Protection Committee, at jlthauge@mmm.com.

Resources In the 1980s, the AIHA Journal published several letters to the editor that discussed the importance of standard terminology for respiratory protection. The letters appeared in three issues: December 1982, page A16; March 1983, pages B24–25; and March 1983, pages B25–26.
The AIHA Journal also published previous versions of the Respirator Performance Terminology as letters to the editor. The first version appeared in the May 1985 issue, page B22, and the second version appeared in the March/April 2002 issue, page 132.
Additional sources of information on respiratory protection terminology include:
  • Journal of the International Society for Respiratory Protection: “Field test of powered air purifying respirators at a battery manufacturing facility” (January 1986).
  • Los Alamos Scientific Laboratory: “Respirator Protection Factors,” Report No. LA-6084-MS (1976).
New Terminology for Respiratory Protection
What's in a
Public support for legalizing marijuana has reached an all-time high in Gallup Polling with 58 percent of Americans supporting the movement. Last January, Fox News reported the stock price for a medical marijuana machine company increased 57 percent after Colorado legalized recreational use. The state reported over $5 million in taxed and regulated sales of marijuana during the first week of legalization and more than $200 million during the first four months. - Eric Nelson and Jeremy Slagley