Collecting "Samples" with Direct-Reading Instruments
By Kay Bechtold
June 18, 2026—Two speakers from OSHA would like to see employers use personal direct-reading monitors as more than warning devices. During an educational session on June 2 at AIHA Connect, Phil Smith, PhD, CIH, FAIHA, director of the OSHA Technical Center, and Todd Jordan, MSPH, CIH, director of OSHA’s Health Response Team, explained that data from these life-saving devices should also be treated as “samples”—digital records of exposures to be used by occupational and environmental health and safety professionals to identify hazards and protect workers. In most cases, employers are already using personal gas and vapor monitors to alert workers of hazardous conditions, Smith said. But a better approach, he added, would be for employers to routinely review information they already have by gathering these instruments and downloading the exposure data.
“Employers can do a lot of good for their employees if they start looking at the data, especially in highly hazardous industries,” he said.
Many of these devices will record exposures for an entire workday, and, in some cases, multiple workdays, before they start to overwrite old data, allowing OEHS professionals to examine exposures over the course of a day as well as how exposures vary from day to day. According to Smith, it’s “really only [possible to] see these intra-workday fluctuations with direct-read devices.” This kind of equipment can also be particularly useful when working to identify peak exposures or when immediately dangerous to life or health (IDLH) concentrations or conditions are possible, he continued.
OSHA now has validated methods for using direct-reading instruments and sensors to monitor for carbon monoxide, carbon dioxide, hydrogen sulfide, nitric oxide, and chlorine. Smith added that the agency is working on a method for ozone.
“Ozone isn’t such a dangerous analyte, but we don’t have a very good traditional sampling method for it, so we’re hoping to fix that with a direct-reading instrument,” he said.
Smith shared an example of measuring hydrogen sulfide exposures with a personal gas monitor using OSHA’s method. In three different instances, exposures exceeded the agency’s 50 ppm peak exposure for hydrogen sulfide.
“It’s not possible in any sense that a 15-minute [time-weighted average] would be able to capture this exceedance,” Smith said. “First you have to figure out which 15 minutes to sample, and even if you could magically know when the exposure occurred, you’re going to get an average” below the current OSHA permissible exposure limit.
Smith turned the session over to Jordan, who presented several case studies from OSHA investigations involving carbon dioxide, carbon monoxide, and hydrogen sulfide exposures, illustrating how the use of these methods for real-time monitoring identified exceedances of IDLH values, PELs, and ceiling limits.
One of Jordan’s examples focused on a complaint inspection of a coffee manufacturing facility in which carbon monoxide exposures and inadequate ventilation were the main concerns. When OSHA’s compliance safety and health officer (CSHO) initially arrived at the facility, the power was out and the operation was down, making sampling impossible. By the time of OSHA’s return visit, the employer had set up some fans that generated what Jordan described as “a gale wind, like employees were in a hurricane.” Despite the added controls, the CSHO noticed that her personal meter was consistently showing above 100 ppm for carbon monoxide, prompting her to back out of the operation and observe. When she noted a reading over the IDLH value, she called Jordan and Smith, and the team ultimately decided to shut down the operation. The TWA for the sampling period of the visit—while cut short due to the shutdown of the facility—was over 100 ppm, which is more than double the PEL, Jordan noted. Results from direct-reading monitors showed a maximum exposure of 1,730 ppm, or almost one and a half times the IDLH value.
“We would never have found this with any of our other sampling methods,” Jordan said.
Direct-reading instruments also helped OSHA find peak exposures at a facility that manufactured protein from inedible poultry. This inspection also stemmed from a complaint, with workers alleging that they were overexposed to hydrogen sulfide when opening truck trailers and that the alarms of hydrogen sulfide detectors were ignored. Jordan shared that the complaint originated from the drivers, “who you would think would not have high exposures because their work in and around the trucks is pretty limited,” he said. But according to the workers, their worst exposures were in the summer, when the tanks they collect bake in the sun, which produces more hydrogen sulfide. OSHA sampled during the fall and winter—in what Jordan described as likely “the best-case scenario” given the season—and still measured overexposures, with the worst being 40 ppm, or double OSHA’s ceiling limit for hydrogen sulfide. These exposures were found at limited times during loading and unloading, he said, demonstrating that the “type of data you get with DRIs is invaluable for finding peak exposures.”
Jordan’s examples—which also included investigations of workplaces in refrigerated warehousing and storage, animal slaughtering, and oil and gas—were intended to show that hazardous atmospheres can develop across a number of different industries. In several instances, employers knew they had hazards and weren’t reviewing results from their real-time monitoring, Jordan said. He encouraged employers to “start by looking at the data.”
“We don’t have a standard that says you have to do this,” Smith clarified, but “I think you should do it—we’re showing the way to do it.”
Kay Bechtold is managing editor of The Synergist.