Industrial Hygiene Program: Air Monitoring, Exposure Assessment, and Building an IH Program

Safety programs prevent injuries. Industrial hygiene programs prevent disease. The distinction matters because occupational disease is silent. A worker doesn’t collapse from silicosis the day they first grind concrete. It develops over years of exposure that could have been measured and controlled. By the time symptoms appear, the damage is done.

Industrial hygiene is the science of anticipating, recognizing, evaluating, and controlling workplace hazards that cause illness rather than injury. Those four words, anticipation, recognition, evaluation, control, are the professional framework the field runs on. They’re worth understanding before you build any kind of IH program.

The Four Core Functions

Anticipation means identifying hazards before workers are exposed. When a new process comes online, when a new chemical gets introduced, when a job task changes, the IH function is supposed to be in the room before the work starts. Not after the first round of monitoring shows elevated exposures.

Recognition is the identification of actual hazards in current operations. That means knowing which chemicals your workers use and which ones have meaningful exposure potential. It means knowing which job tasks generate dust, vapor, or noise above thresholds you care about. A GHS safety data sheet gives you the starting point, but it doesn’t tell you what the actual airborne concentration is at the worker’s breathing zone during a specific task.

Evaluation is measurement. It’s where air sampling, noise dosimetry, and biological monitoring come in. You can’t manage what you haven’t measured, and assumptions about exposure levels are almost always wrong.

Control is what you do about it. IH programs that stop at evaluation and hand out respirators have skipped the most important step.

Exposure Assessment: Where the Program Actually Starts

Before you can sample anything, you need to know who is exposed and to what. That’s the exposure assessment phase.

Industrial hygienists use similar exposure groups, or SEGs, to organize this work. A SEG is a set of workers who have roughly equivalent exposures because they do the same tasks, in the same location, with the same materials and controls. A spray painter in a paint booth is a different SEG from a painter doing touch-up work in an open warehouse. Grouping workers this way lets you sample a representative subset rather than monitoring every individual, which makes the program feasible.

AIHA’s occupational exposure assessment framework, which is the industry standard approach, uses SEGs as the building block for all monitoring decisions. You identify the SEGs, rank them by likely exposure relative to the occupational exposure limit, and prioritize monitoring accordingly. High-priority SEGs get sampled first. Low-priority groups may not need monitoring at all if exposure potential is clearly negligible.

The qualitative assessment that drives SEG prioritization is itself a skill. You’re looking at factors like how much of the substance is used, how volatile or dusty it is, the size of the work area, ventilation, and the duration of exposure. Get this step right and your monitoring budget goes to the exposures that matter.

OSHA PELs vs. ACGIH TLVs

This distinction trips up a lot of safety professionals who haven’t worked with IH before.

An OSHA PEL, Permissible Exposure Limit, is a legally enforceable airborne concentration limit. If exposure exceeds the PEL, you have an OSHA violation. Most OSHA PELs were set in 1971 and have never been updated. OSHA attempted a major PEL update in 1989 and most of those changes were vacated by court challenge in 1992. The result is that many OSHA PELs are based on decades-old toxicology data and don’t reflect what’s currently known about health effects at those concentrations.

An ACGIH TLV, Threshold Limit Value, is a recommended exposure guideline published annually by the American Conference of Governmental Industrial Hygienists. TLVs are updated every year based on current research. For most substances, the TLV is more protective than the OSHA PEL, often by a factor of two to ten. Some OSHA PELs have no corresponding TLV, and some TLVs cover substances OSHA hasn’t set a PEL for at all.

In practice, industrial hygienists use TLVs as their working target. The OSHA PEL is the legal floor. If you’re at or above the TLV but below the PEL, you probably don’t have an OSHA citation risk, but you likely have a health risk you should address.

Use TLVs as your program benchmark. Use PELs to understand your legal exposure. They’re answering different questions.

Air Monitoring: Area vs. Personal Sampling

There are two basic approaches to air monitoring, and they tell you different things.

Personal sampling puts the sample collection device at the worker’s breathing zone, typically a pump and collection media worn on the lapel or collar. Personal sampling measures actual worker exposure during the task. This is what OSHA standards require when monitoring is needed for compliance purposes. It’s also what the AIHA exposure assessment framework treats as the definitive measurement.

Area sampling places sampling equipment at a fixed location in the work area. It measures contamination in a general area rather than at the breathing zone of a specific worker. Area sampling is useful for source identification, for evaluating ventilation effectiveness, and for routine screening. But area samples can’t substitute for personal samples when you’re making compliance determinations.

The choice between them isn’t either/or. A well-designed monitoring program uses area sampling to characterize the general environment and personal sampling to measure actual worker dose.

For substances covered by specific OSHA standards, the standard itself specifies the monitoring method. The silica standard at 29 CFR 1910.1053, for example, spells out methods, frequency, and what to do when exposures are above the action level. Read the standard before you design the monitoring program.

Noise Dosimetry

Noise is the most commonly overexposed occupational hazard in manufacturing environments. A hearing conservation program is required under 29 CFR 1910.95 when workers are exposed to noise at or above 85 dBA as an 8-hour time-weighted average, the action level.

Noise dosimetry measures a worker’s actual noise dose over the work shift. A dosimeter is a small device worn at the shoulder that continuously measures and logs sound levels throughout the shift. The result is a percent dose and an 8-hour TWA.

One noise survey is not enough for most operations. Noise levels change with production rates, equipment maintenance status, and facility layout changes. A program that was surveyed five years ago and hasn’t been revisited since has an unknown current status. Annual dosimetry for workers near the action level is the standard practice.

The hierarchy of controls applies to noise the same way it applies to chemical hazards. Engineering controls first: enclosures, isolation, quieter equipment. Administrative controls second: limiting exposure duration, scheduling loud tasks when fewer workers are present. Hearing protection (PPE) is the last resort, not the first response. If your hearing conservation program is only handing out earplugs, it’s not a program. It’s liability management.

The Hierarchy of Controls in IH

Every IH textbook covers the hierarchy of controls, but the field has a specific context for applying it that’s worth stating clearly.

Elimination and substitution are the most effective controls. Swapping a more hazardous solvent for a less hazardous one is a substitution. Changing a process to eliminate a step that generates dust is an elimination. These changes remove the hazard rather than managing exposure to it. They’re also often the most difficult to implement in existing operations.

Engineering controls are the next tier. Local exhaust ventilation, enclosures, and process isolation control exposure at the source without requiring worker behavior change. They work around the clock and don’t depend on compliance. A properly designed exhaust hood on a grinding station provides more consistent protection than any respirator.

Administrative controls include job rotation, work practice standards, and scheduling changes. They reduce exposure by limiting how long or how often workers contact the hazard. They depend on consistent human behavior to work, which makes them less reliable than engineering controls.

PPE is the bottom of the hierarchy, not the default. A respiratory protection program has significant ongoing costs: fit testing, medical evaluations, training, maintenance, and replacement. Before you go down that road, make sure you’ve genuinely evaluated whether engineering controls can solve the problem.

When to Hire a Consulting IH vs. Staff IH

For most small and mid-size operations, a consulting industrial hygienist is the right answer. A qualified consulting IH can conduct baseline exposure assessments, design a monitoring program, interpret results, and recommend controls. Depending on the complexity of your operation, you might need a consulting engagement once every one to three years for stable processes with no major changes.

Staff IH makes sense when you have complex, ongoing exposure concerns, when OSHA standards require frequent monitoring, or when your operation involves multiple regulated substances with different monitoring requirements. Chemical plants, pharmaceutical manufacturers, mining operations, and large refineries typically have IH staff.

The industrial hygienist career path requires specialized education and, at the senior level, the Certified Industrial Hygienist credential. The CIH certification from the American Board of Industrial Hygiene is the professional standard. It requires an industrial hygiene-related degree, professional experience, and a comprehensive exam. When you’re hiring a consulting IH firm, CIH credentials on the staff who will actually do your work matter.

Building the Program

An IH program isn’t just a monitoring schedule. It’s a documented system with identified exposure groups, a prioritized monitoring plan, written procedures for collecting and analyzing samples, a process for communicating results to workers, and a mechanism for tracking corrective actions.

Workers have the right to know their exposure results. Several OSHA substance-specific standards, including the silica and lead standards, require employers to notify workers when monitoring results exceed action levels. But communicating results shouldn’t be limited to situations where a standard requires it. Workers who understand their exposure levels are more likely to use controls correctly.

The program should also have a change management trigger. New chemical introductions, process modifications, or equipment changes should automatically kick off an IH review before the change goes live. Most exposure incidents happen because someone changed a process and nobody thought to ask whether it created a new hazard.

Start with your highest-risk operations. Map your SEGs. Sample the priority groups. Evaluate results against TLVs, not just PELs. Apply controls starting from the top of the hierarchy. Document everything.