A Certified Industrial Hygienist (CIH) is a credentialed professional who specializes in identifying, evaluating, and controlling workplace health hazards. The certification is issued by the Board for Global EHS Credentialing (BGC) and requires a combination of education, at least four years of professional experience, and passing a comprehensive exam. With roughly 6,800 active credential holders, it’s one of the more selective certifications in occupational health and safety.
What a CIH Actually Does
Industrial hygienists are the people who figure out whether a workplace is making anyone sick, and if so, how to fix it. Their job sits at the intersection of science, engineering, and public health. On any given day, a CIH might be sampling the air in a manufacturing plant for chemical vapors, measuring noise levels on a construction site, evaluating ventilation systems in an office building, or assessing whether workers handling radioactive materials have adequate shielding.
The scope is broad. CIHs deal with indoor air quality problems (like sick building syndrome), asbestos exposure, pesticide safety, repetitive stress injuries, radiation from electromagnetic fields, lead contamination, and hazardous waste management. They also handle emergency response planning and help set exposure limits for chemical and physical agents. Their core responsibilities include:
- Hazard identification: Anticipating, recognizing, and investigating current and emerging workplace risks
- Exposure assessment: Measuring how much of a harmful substance or physical stressor workers actually encounter
- Risk analysis: Determining whether exposure levels are dangerous and who’s most affected
- Control recommendations: Designing or recommending engineering solutions like ventilation systems, noise barriers, or radiation shielding
- Program management: Aligning health and safety programs with an organization’s operational and financial goals
A CIH functions primarily as an adviser. They make recommendations, set internal standards, and build the business case for safety interventions. Many work directly with senior leadership to integrate industrial hygiene into an organization’s broader risk management strategy.
Where CIHs Work
Industrial hygienists aren’t confined to factories. They work across a wide range of industries: chemical companies, manufacturing plants, hospitals, government agencies, public utilities, agricultural operations, research laboratories, colleges and universities, insurance companies, labor unions, consulting firms, and hazardous waste companies. Some work in-house for a single employer. Others work for consulting firms, moving between client sites and tackling different types of hazards each week.
How to Become a CIH
The certification path has several layers. You need a bachelor’s degree or higher, with at least 60 semester hours in science, math, engineering, or science-based technology (15 of those hours at the junior, senior, or graduate level). Degrees in biology, chemistry, physics, or engineering are accepted directly. Other bachelor’s degrees can qualify if they include enough relevant coursework. Graduates of programs accredited by ABET, the main accreditor for applied science and engineering programs, also qualify.
Beyond the degree, you need 180 academic hours (or 240 continuing education contact hours) of industrial hygiene coursework, with at least half covering fundamentals, toxicology, measurements, and controls. You also need a minimum of two contact hours in ethics.
Experience matters just as much as education. Candidates must document at least 48 months (four years) of professional-level industrial hygiene work, supported by at least two references, one of whom is a practicing CIH. Graduates of ABET-accredited programs get a small break: a master’s degree knocks the requirement down to 36 months, and a bachelor’s to 42 months.
Finally, you have to pass the CIH comprehensive exam. Half the exam covers exposure assessment principles, including toxicology, air sampling, analytical methods, and biostatistics. Another 35% tests your ability to select, design, and validate controls like ventilation systems, noise abatement, radiation shielding, and personal protective equipment. The remaining portion covers program management, ethics, and communication.
What the Exam Covers
The exam tests 16 subject areas: air sampling and instrumentation, analytical chemistry, basic science, biohazards, biostatistics and epidemiology, community exposure, engineering controls and ventilation, ergonomics, health risk analysis and hazard communication, program management, noise, non-engineering controls, ionizing and non-ionizing radiation, thermal stressors, toxicology, and work environments and industrial processes. It’s designed to confirm that a candidate has broad, working knowledge across the full scope of industrial hygiene, not just expertise in one narrow area.
Toxicology shows up repeatedly throughout the exam blueprint. You’re expected to apply concepts like dose-response relationships, acute versus chronic exposure, latency periods, and routes of entry (inhalation, skin absorption, ingestion) to real-world scenarios. Ventilation design, noise measurement, and radiation protection are also heavily tested, both in terms of theory and hands-on survey skills like calculating air flow parameters or performing noise and vibration assessments.
Keeping the Certification Active
Earning the CIH isn’t a one-time event. Credential holders must complete continuing education on a 60-month (five-year) cycle. The required hours span industrial hygiene practice, ethics, and general management or leadership topics. BGC places no restrictions on the career paths a CIH can pursue, so credential holders can specialize, shift industries, or broaden their scope over time, as long as they meet the ongoing maintenance requirements.
Salary and Career Outlook
The average base salary for professionals holding a CIH credential is approximately $121,000 per year, based on Payscale survey data. Actual earnings vary depending on industry, location, years of experience, and whether you work as a consultant or in-house. The credential carries significant weight in hiring and promotion decisions because of the rigorous requirements to earn and maintain it. With fewer than 7,000 active CIHs, demand for qualified professionals tends to outpace supply in many industries.