Today's personal protective equipment (PPE) includes clothing, helmets, respirators, goggles and other gear to reduce exposures the wearer experiences from chemicals, heat, electrical hazards, infection and more.
One aspect of PPE, respiratory protection, has been used for hundreds of years. As far back as the first century, Pliny the Elder described a filtering device for use against vermillion dust. Leonardo da Vinci (1452-1519) was concerned with providing respiratory protection against chemical warfare agents and suggested using a wet cloth. Also in the 16th century, Agricola described the respirator-like devices used in mines.
In the United States, as in Europe in the 18th and 19th centuries, the search for respiratory protection centered on the fire services. Firemen often were required to have a full beard. They would soak their beards with water and clamp them in their teeth before going into a smoke-filled area in an effort to block some of the larger airborne particulates.
The first U.S. patent for an air-purifying respirator was granted on June 12, 1849 to Lewis P. Haslett. The Haslett's Lung Protector used a moistened wool filter or similar porous material and one-way clapper valves to filter dust.
As late as early last century, fire departments still had few options for respiratory protection devices. In 1910, former firefighter Robert Wells described the Berkeley, Calif. department's methods for combating smoke inhalation. “The boys used to have a plug of tobacco … they would chew in their mouth to breath less smoke and drink ample amounts of steam beer afterward to cleanse their lungs.”
In the 20th century, as technology improved, government regulations were enacted to protect the safety and health of workers, particularly those in high-risk industries such as mining. At various times, these regulations have driven innovation, and sometimes innovation has exceeded what the regulations require, eventually resulting in changing regulations.
At times, regulations have been the impetus for the development of increasingly advanced technologies and created the incentive for companies to develop new, state-of-the-art respiratory protection products. In countries that lack an effective regulatory structure, workers and citizens are taking responsibility to protect their health, occasionally using makeshift respiratory protection devices when nothing else is available.
Congress established the United States Bureau of Mines (USBOM) in 1910, following a decade in which the number of coal mine fatalities exceeded 2,000 annually. The bureau was charged with conducting research and working with mining companies to adopt improved safety procedures to help reduce accidents in the coal mining industry. (By comparison, from 2003 to 2005, an average of 25 fatalities per year occurred in U.S. coal mines.)
At the time of World War I, gas masks were developed to protect soldiers from chemical warfare agents. These were rubber facepieces fitted with charcoal cartridges or particulate filters. Soon, this technology could be used in industry to protect workers, and in 1919, the USBOM began approving respiratory protective devices for use in industrial and mining workplaces.
In the 1930s, America's greatest industrial catastrophe occurred when over 470 workers died from exposure to silica dust while building a tunnel in Gauley Bridge, W.Va. In addition, as many as 1,500 workers were disabled from silicosis.
These workers worked without any measures to control the dust, such as dust masks, respirators, mine ventilators or dust suppressors. Congressional hearings were held, and the findings of these hearings spurred calls for greater oversight of mine worker safety and resulted in several decades of health and safety legislation.
By 1938, the predecessor to the American National Standards Institute published a standard (ASA Z2) to guide occupational health and safety managers on the use of respiratory protection. As with many early OSHA standards, the respirator regulation later promulgated by the agency largely was based upon the subsequent ANSI guidance standard.
In the 1950s, the USBOM expanded its approval schedules for many types of respirators as published in Title 30 in the Code of Federal Regulations. In subsequent years, two federal acts (the U.S. Federal Coal Mine Safety Act and the U.S. Federal Metal and Nonmetallic Mine Safety Act) were enacted to improve mine safety. At this time, respirator use still was focused on workers in the mines and the military.
DUST MASKS AND RESPIRATORS
In the late 1950s, a large medical products manufacturer that was selling surgical masks considered entering the industrial market. However, surgical masks, then and now, are designed to protect the patient from the doctor's germs but do not protect the wearer from particles in the air.
By the early 1960s, a team looking to develop new products took those surgical masks to industries in their area, and asked if they could use a similar device for filtering airborne particles in the workplace. As the team listened to these potential customers, members realized there was a definite need for an inexpensive, easy-to-use dust mask for industry.
The device developed had a simple design, consisting of a nonwoven fiber cup, an adjustable metal nose clip and a strap that secured the dust mask to the wearer's face. In the early 1960s, the dust mask was introduced for use against non-harmful particles. However, the need still existed for a more comfortable, government-approved respirator that workers could wear all day.
In the late 1960s, development was underway of a single use (filtering facepiece) respirator that was more comfortable and more readily accepted by workers, and that could meet the approval requirements of the USBOM. In the early 1970s, the design of a filtering facepiece respirator was advancing, but there still were two things missing: USBOM approval schedules for filtering facepiece respirators and regulations governing the use of respiratory protection in general industry.
The Occupational Safety and Health Act of 1970 (OSH Act) marked the beginning of a new era in the history of public efforts to protect industrial workers from harm on the job. The act established a federal program designed to protect workers from job-related death, injury and illness. The Department of Labor established the Occupational Safety and Health Administration (OSHA) to implement the act. OSHA published several standards in 1972, including the General Respiratory Protection Standard (1910.134) that regulates the use of respiratory protection in the workplace. Today, 29 CFR 1910.134 mandates that employers have a complete written respiratory program including medical evaluation, fit testing, training and recordkeeping.
In 1971, the National Institute for Occupational Safety and Health (NIOSH) was created. Among other tasks, NIOSH was charged with testing and certifying respirators. The respirator approval schedule at the time, however, did not include approval criteria for filtering facepiece particulate respirators, because a filtering facepiece device had not been developed that could meet all the requirements for particulate respirators. Development of filtering facepiece devices with higher efficiency filters prompted NIOSH, in cooperation with the USBOM, to create approval criteria for filtering facepiece respirators, which were referred to as single-use respirators.
In March 1972, approval criteria for single-use respirators was published in the Federal Register and incorporated as 30 CFR Part 11.8. These criteria allowed single-use respirators to be approved for respiratory protection against pneumoconiosis and fibrosis-producing dusts and mists, including but not limited to aluminum, asbestos, coal, flour, iron ore and free silica. Shortly thereafter, the first approved single-use particulate respirator in the United States was introduced.
In the late 1970s, a filtering facepiece respirator was launched. It featured a valve that allowed the wearer to easily exhale humidity. Previously, the only respirators with a valve were rubber facepieces that required regular cleaning and maintenance.
This new filtering facepiece improved wearer comfort in high heat and humidity conditions — a critical factor in how long respirators are worn on the job. Many workers found filtering facepiece respirators more comfortable than the rubber facepiece that currently were available. In addition, employers appreciated the increased worker acceptance and lack of maintenance.
TECHNOLOGY DRIVES REGULATIONS
Initially, all particulate filtering facepiece respirators met the requirements to be “single-use dust respirators.” As filter technology improved, filtering facepiece respirators could be approved as reuseable filters as well. Filtering facepieces approved to these criteria could be used in a broader range of industries, such as those with exposure to cadmium and lead. Respirator manufacturers also were finding ways to make filter media easier to breathe through.
Another example of technology driving regulations is the development and later requirement for cartridge change schedules. Organic vapor cartridges historically were limited to those vapors having good warning properties and were replaced when the respirator wearer detected, or smelled, the vapor. Then a predictive model was developed to determine the service life of cartridges for organic vapors.
OSHA later accepted this concept, which encouraged manufacturers to provide a method to calculate cartridge service life. This resulted in an OSHA-required change schedule in the workplace and expanded air-purifying respirators use to organic vapors with poor warning properties. A key manufacturer developed the first user-friendly version to help employers easily determine cartridge service life.
The filter efficiency tests for particulate respirators were published in the mid-1950s using test equipment available at that time. Each test was lengthy and by the 1990s, it was recognized that new testing technology and new applications existed and that the respirator approval criteria could be updated.
REGULATIONS DRIVE TECHNOLOGY
In 1994, NIOSH published new respirator regulations — 42 CFR 84 — that incorporated new particulate filtration tests. These tests created nine classes of particulate filter approval with minimum efficiency levels ranging from 95 percent to 99.97 percent efficiency against a very demanding particle size of approximately 0.3 micron mass median aerodynamic diameter (MMAD) particles. Silica was replaced by sodium chloride (for N-series respirators) and an oily aerosol [dioctyl phthalate (DOP)] (for R- and P-series respirators) as the test aerosols.
These new regulations posed a challenge to several leading manufacturers because the filter media used in many of their 30 CFR Part 11 respirators wouldn't meet parts of the new NIOSH standard without increasing the amount of filter media utilized. This could result in a less comfortable respirator. In addition, the oily mist test aerosol was especially challenging for some filter media.
Respirator manufacturers were looking for ways to create respirators that had the lowest breathing resistance (for comfort) and still meet the new respirator regulations. Based on technology developed in the 1950s in the U.S. Naval Research Laboratory, developers knew that filter media made from melt-blown polymer fibers was excellent at retaining an electrostatic charge — and was more consistent and permanent than resin wool.
In the 1970s, manufacturers were using electrostatically charged polymer fibers for filter media to increase filter efficiency. Using less filter media allowed respirators to be lighter and more comfortable. This is important, because proper fit and comfort are key factors in whether respirators are worn and for how long. Wearing a respirator the entire time a worker is in a contaminated area is essential to reducing their exposure to hazardous airborne substances.
Over the years, scientists have made many advances to enhance the electrostatic charge and prolong the charge on fibers. They also learned to incorporate carbon particles into the non-woven media, thereby helping reduce nuisance levels of gases and vapors.
During the 1990s, scientists developed better polymers and new charging processes for fibers. In addition, additives were incorporated that reduced the effect of oily mist on charged fibers.
As the pressure drop of filter media was decreased, exhalation valves changed as well. Researchers developed an ingenious new valve for respirators. The innovative shape opens very easily during exhalation. An easy-opening valve allows hot air and humidity to escape from the respirator more efficiently and improves user comfort.
Previously, many people believed it was impossible to create a valve that could open under such low pressure. The scientists proved skeptics wrong — and the valve design now is protected by eight U.S. patents. The overall result of the 42 CFR 84 regulations was development of new respirators featuring enhanced comfort features and updated designs that met the new testing requirements.
Some developing countries do not have respirator performance or use standards. Through increasing awareness of occupational health and safety issues among employers, workers and governments, respirator regulations will be strengthened and adopted. The International Standards Organization (ISO) currently is developing global respirator performance standards that will be available for all countries to incorporate into their respirator use regulations.
These new performance standards may again pose a challenge to respirator manufacturers and may drive new technologies. In addition, as the population of respirator users expands, respiratory product developers will need to consider designing respirators for an even wider variety of faces.
While engineering controls always are the first choice to eliminate or reduce a hazard, respiratory protection has been in use for years and will continue into the future. Health and safety professionals working together with agencies such as NIOSH and OSHA, and with international organizations such as ISO, will continue to promote the development of new respirator technology, designs and both performance and use regulations to help protect workers around the world.
Bill Herris, global brand manager, 3M Occupational Health and Environmental Safety Division, has worked in various capacities in the respiratory protection business for over 39 years.