Certification Practice Exam Questions

OSHA Hydrogen Sulfide (H₂S) Safety Certification Practice Exam Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

Question 1: What is the primary route of exposure to hydrogen sulfide?

• Skin contact
• Inhalation
• Ingestion
• Eye contact

Answer: B

Rationale: Hydrogen sulfide is a gas, and inhalation is the most common and

dangerous route of exposure, affecting the respiratory system and nervous system. 1 / 4

Question 2: What is the characteristic odor of low concentrations of

hydrogen sulfide?

• Fruity
• Chlorine-like
• Rotten eggs
• Ammonia

Answer: C

Rationale: Hydrogen sulfide has a distinct “rotten egg” smell at low

concentrations, but high levels can deaden the sense of smell.

Question 3: Which of the following symptoms may indicate hydrogen sulfide

exposure?

• Skin rash
• Headache and nausea
• Hair loss
• Fever

Answer: B

Rationale: Early exposure can cause headache, dizziness, nausea, and

irritation of eyes and respiratory tract.

Question 4: At what concentration of H₂S does OSHA consider it

immediately dangerous to life or health (IDLH)?

• 10 ppm
• 50 ppm
• 100 ppm 2 / 4

• 100 ppm

Answer: D

Rationale: IDLH for hydrogen sulfide is 100 ppm, meaning exposure at or

above this level can be fatal or cause permanent health effects.

Question 5: What type of personal protective equipment (PPE) is required

when entering a high H₂S area?

• Standard gloves
• Respiratory protection, such as SCBA
• Hard hat only
• Safety glasses

Answer: B

Rationale: Self-contained breathing apparatus (SCBA) or supplied-air

respirators are required in environments with high H₂S concentrations.

Question 6: Hydrogen sulfide is heavier than air. Where is it most likely to

accumulate?

• At the top of a room
• Evenly throughout the space
• In low-lying areas or pits
• In ventilation ducts

Answer: C

Rationale: Being heavier than air, H₂S tends to settle in confined, low-lying

areas, posing a risk of undetected exposure. 3 / 4

Question 7: Which type of gas detector is commonly used for H₂S

monitoring?

• Carbon monoxide detector
• Oxygen sensor
• Electrochemical sensor
• Smoke detector

Answer: C

Rationale: Electrochemical sensors are designed to detect H₂S

concentrations in air and trigger alarms at preset levels.

Question 8: What is the OSHA permissible exposure limit (PEL) for H₂S over

an 8-hour workday?

• 5 ppm
• 10 ppm
• 20 ppm
• 50 ppm

Answer: C

Rationale: OSHA sets the PEL for hydrogen sulfide at 20 ppm as a ceiling

limit over an 8-hour shift.

Question 9: Which of the following is a key component of an H₂S safety

plan?

• Fire extinguisher maintenance
• Emergency response procedures
• Noise control measures
• / 4