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A safety technician measures a chemical concentration of 250 ppm. What does "ppm" stand for?

Parts per million

Percent per milliliter

Pressure per minute

Particles per meter

to track

2026 Statistics

Key Facts: OHST Exam

200

Total Questions

175 scored + 25 unscored

~66%

Passing Score

109 of 175 scored

4 hrs

Exam Duration

BCSP

$440

Total Fee

$140 app + $300 exam

31.4%

Hazard ID Domain

Largest domain

5 years

Recertification Cycle

20 points required

The OHST exam has 200 questions (175 scored + 25 unscored) in 4 hours. Seven domains: Hazard Identification & Control (31.4%), Safety/Health/Environmental Programs (18.3%), Industrial Hygiene (14.3%), Communication & Training (13.7%), Math/Science/Business (9.7%), Emergency Preparedness (7.4%), and Ethics (5.2%). Requires 3 years occupational safety experience. $440 total fee.

Sample OHST Practice Questions

Try these sample questions to test your OHST exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 200+ question experience with AI tutoring.

1A safety technician measures a chemical concentration of 250 ppm. What does "ppm" stand for?

A.Parts per million

B.Percent per milliliter

C.Pressure per minute

D.Particles per meter

Explanation: PPM stands for "parts per million" and is a common unit of measurement in industrial hygiene for expressing very dilute concentrations of substances. One ppm is equivalent to 1 part solute per 1 million parts solvent. For gases, 1 ppm is often equivalent to 1 mg/m3 at standard temperature and pressure.

2A company experiences 4 recordable injuries in a quarter with 250,000 total hours worked. What is the Total Recordable Incident Rate (TRIR)?

A.1.6

B.3.2

C.6.4

D.8.0

Explanation: The TRIR formula is: (Number of recordable injuries x 200,000) / Total hours worked. Using this formula: (4 x 200,000) / 250,000 = 800,000 / 250,000 = 3.2. The 200,000 constant represents the equivalent of 100 full-time workers (40 hours/week x 50 weeks x 100 workers).

3What is the primary difference between an acute exposure and a chronic exposure to a hazardous substance?

A.Acute exposures occur over short periods; chronic exposures occur over extended periods

B.Acute exposures affect only the lungs; chronic exposures affect all organs

C.Acute exposures are always fatal; chronic exposures are never fatal

D.Acute exposures require immediate treatment; chronic exposures do not require treatment

Explanation: Acute exposure refers to a single exposure or multiple exposures occurring over a short period (typically 24 hours or less), often resulting in immediate or rapid-onset health effects. Chronic exposure refers to repeated exposures over an extended period (months to years), which may lead to delayed or cumulative health effects. Both types of exposure can be serious and may require medical treatment.

4A facility has direct costs of $50,000 from an accident and indirect costs estimated at 4 times the direct costs. Using the standard indirect cost multiplier, what are the total accident costs?

A.$200,000

B.$250,000

C.$300,000

D.$400,000

Explanation: Total accident costs = Direct costs + Indirect costs. Given direct costs of $50,000 and indirect costs of 4 x $50,000 = $200,000, the total costs are $50,000 + $200,000 = $250,000. OSHA estimates that indirect costs typically range from 1.1 to 4.5 times direct costs, depending on the industry and severity of the incident.

5In the context of Process Safety Management (PSM), what is the significance of the lower flammability limit (LFL)?

A.It indicates the minimum concentration of a flammable gas or vapor in air below which propagation of flame does not occur

B.It represents the maximum safe storage temperature for flammable liquids

C.It defines the minimum oxygen level required for combustion

D.It specifies the maximum concentration before an explosion occurs

Explanation: The Lower Flammability Limit (LFL), also known as the Lower Explosive Limit (LEL), is the minimum concentration of a flammable gas or vapor in air below which a flame will not propagate. Concentrations below the LFL are considered "too lean" to burn. The Upper Flammability Limit (UFL) represents the maximum concentration above which the mixture is "too rich" to burn. Both limits are critical for PSM hazard assessments.

6According to the hierarchy of controls, which control method is generally considered most effective?

A.Personal protective equipment (PPE)

B.Engineering controls

C.Elimination

D.Administrative controls

Explanation: The hierarchy of controls, in order from most to least effective, is: 1) Elimination (removing the hazard entirely), 2) Substitution (replacing with less hazardous materials/processes), 3) Engineering controls (isolating people from hazards), 4) Administrative controls (changing work procedures), and 5) PPE (protecting the individual). Elimination is always the preferred approach as it completely removes the hazard.

7What is the primary purpose of a Job Hazard Analysis (JHA)?

A.To identify hazards associated with each step of a job and develop controls

B.To document employee attendance and punctuality

C.To calculate workers compensation insurance premiums

D.To determine appropriate salary levels for job positions

Explanation: A Job Hazard Analysis (JHA), also called Job Safety Analysis (JSA), is a technique that focuses on job tasks to identify hazards before they occur. It involves breaking down a job into specific steps, identifying hazards associated with each step, and developing controls to eliminate or reduce the hazards. JHAs are proactive tools for preventing workplace injuries and illnesses.

8Under the Globally Harmonized System (GHS) of Classification and Labeling of Chemicals, what information is required on a chemical label?

A.Only the chemical name and manufacturer address

B.Product identifier, signal word, hazard statement, pictogram, precautionary statement, and supplier identification

C.Only the expiration date and storage requirements

D.Only the price and barcode

Explanation: GHS requires six core elements on chemical labels: 1) Product identifier (chemical name), 2) Signal word ("Danger" or "Warning"), 3) Hazard statement(s) describing the nature of hazards, 4) Pictogram(s) representing the hazard visually, 5) Precautionary statement(s) describing protective measures, and 6) Supplier identification with name, address, and telephone number.

9During an incident investigation, which approach focuses on identifying system failures rather than assigning blame to individuals?

A.Punitive investigation

B.Root cause analysis

C.Disciplinary review

D.Performance evaluation

Explanation: Root cause analysis is a systematic process for identifying the underlying causes of incidents, focusing on system failures, inadequate procedures, and organizational factors rather than individual blame. This approach recognizes that human error is often the result of poorly designed systems or inadequate controls. Effective incident investigations examine contributing factors including equipment, environment, procedures, training, and management systems.

10What is the primary goal of behavior-based safety (BBS) programs?

A.To observe and reinforce safe behaviors while correcting unsafe behaviors

B.To eliminate all workplace hazards through engineering controls

C.To replace human workers with automation

D.To increase production efficiency regardless of safety

Explanation: Behavior-based safety (BBS) programs focus on identifying and reinforcing safe behaviors through observation, feedback, and positive reinforcement. BBS recognizes that while hazards should be controlled through the hierarchy of controls, worker behavior plays a critical role in safety outcomes. Effective BBS programs involve employees in observations, provide positive feedback for safe behaviors, and use non-punitive approaches to address at-risk behaviors.

About the OHST Exam

The OHST (Occupational Hygiene and Safety Technician) exam validates competency in hazard identification and control, safety management programs, industrial hygiene, organizational communication, emergency preparedness, and professional ethics. It covers 7 domains with 200 questions (175 scored + 25 unscored).

Questions

200 scored questions

Time Limit

4 hours

Passing Score

~66% (109 of 175 scored)

Exam Fee

$440 ($140 app + $300 exam) (Board of Certified Safety Professionals (BCSP) / Pearson VUE)

OHST Exam Content Outline

31.4%

Hazard Identification and Control

Identify workplace hazards, risk assessment, incident investigation, and hazard control methods

18.3%

Safety, Health, and Environmental Programs

Safety management systems, risk management, regulatory compliance, program implementation

14.3%

Health Hazards and Basic Industrial Hygiene

Chemical, biological, and physical hazards, exposure assessment, sampling methods

13.7%

Organizational Communication and Training

Safety training development, communication techniques, documentation practices

9.7%

Fundamental Math, Science, and Business

Math and science applications in safety, statistics, business calculations

7.4%

Emergency Preparedness, Fire Prevention, Security

Emergency response planning, fire prevention systems, workplace security

5.2%

Ethics and Professional Conduct

BCSP Code of Ethics, professional responsibility, ethical decision-making

How to Pass the OHST Exam

What You Need to Know

Passing score: ~66% (109 of 175 scored)
Exam length: 200 questions
Time limit: 4 hours
Exam fee: $440 ($140 app + $300 exam)

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

OHST Study Tips from Top Performers

1Focus on Hazard Identification and Control (31.4%) — the largest domain covering workplace hazards, risk assessment, and incident investigation

2Master the hierarchy of controls: elimination, substitution, engineering controls, administrative controls, PPE

3Study OSHA standards: general duty clause, recordkeeping (300/300A/301), and common cited standards

4Know industrial hygiene fundamentals: PELs, TLVs, RELs, sampling methods, and exposure assessment

5Review emergency action plans, fire prevention plans, and evacuation procedures

6Understand the BCSP Code of Ethics — this domain (5.2%) appears on every exam and is tested directly

Frequently Asked Questions

What is the OHST certification?

OHST (Occupational Hygiene and Safety Technician) is a BCSP certification for safety professionals with at least 3 years of occupational health and safety experience. It validates competency across 7 domains including hazard identification, safety programs, and industrial hygiene.

How many questions are on the OHST exam?

The OHST exam has 200 questions (175 scored + 25 unscored beta questions) in 4 hours. The passing score is approximately 66% (109 of 175 scored questions). The exam is administered at Pearson VUE test centers.

What are the prerequisites for the OHST exam?

You need 3 years of experience in occupational hygiene or safety with a minimum of 35% of job tasks related to safety. A BCSP-qualified credential (OSHA 10/30, first aid/CPR, etc.) may be needed depending on the application pathway.

How does OHST compare to ASP and CSP?

OHST is designed for technician-level safety professionals with hands-on field experience. ASP (Associate Safety Professional) and CSP (Certified Safety Professional) require more education and broader safety management experience. OHST is often a stepping stone toward ASP/CSP.

How should I prepare for the OHST exam?

Plan for 80-120 hours of study over 6-10 weeks. Focus heavily on Hazard Identification and Control (31.4%) — the single largest domain. Also prioritize Safety Programs (18.3%) and Industrial Hygiene (14.3%). Complete practice exams to build timing skills for the 4-hour test.