STS Practice Questions (2026) — Free Sample Questions with Answers

Answer: B

1. Formula: TRIR = (number of recordable cases × 200,000) / total hours worked.
2. Recordable cases: 1 + 0 + 2 + 1 + 1 + 1 = 6. Hours: 38,000 + 41,000 + 40,000 + 39,000 + 42,000 + 40,000 = 240,000 hours.
3. TRIR = (6 × 200,000) / 240,000 = 1,200,000 / 240,000 = 5.0.
4. Answer: 5.0 recordable cases per 100 full-time workers. Check: 240,000 hours is 1.2 times 200,000, and 6 / 1.2 = 5.0.

2.5: Uses 100,000 hours instead of 200,000 (the base for 100 full-time workers).

5.0: Correct. TRIR = (recordable cases × 200,000) / hours worked = (6 × 200,000) / 240,000 = 5.0.

17.5: Adds the 15 first-aid-only cases to the 6 recordables; first-aid cases are not recordable.

25.0: Uses a 1,000,000-hour base instead of the OSHA 200,000-hour base.

TRIR counts only recordable cases and uses the 200,000-hour base (100 workers × 40 h × 50 weeks).

Answer: B

Hydraulic oil on the floor next to the baler: This is the immediate (direct) cause: the unsafe condition at the moment of the slip.

A work-order system that does not give priority to reported safety hazards: Correct. The root cause is the management-system failure that allowed a known, reported leak to stay unrepaired; fixing it prevents similar incidents elsewhere.

The worker not watching the floor while walking: Blaming the worker's act stops at a surface cause and ignores why the oil was there for a month.

Worn soles on the worker's safety shoes, which reduced traction on the wet floor: A possible contributing factor, but it does not explain why the reported leak was never fixed.

Immediate causes are the unsafe acts or conditions at the event; root causes are the system or management failures behind them.

Answer: C

Keep backing slowly while the backup alarm keeps sounding: An alarm does not tell the driver where the spotter is.

Finish backing using the dock bumpers as a guide: Ignores that the spotter may now be behind the truck.

Stop at once and wait until the spotter is visible again: Correct. Fleet backing rules require the driver to stop whenever the spotter is out of sight; the spotter may be in the vehicle's path.

Sound the horn and continue backing: A horn warns but does not confirm the path is clear.

Fleet safety rests on company practice: pre-trip defects stop the vehicle, spotters stay visible, phones wait until parked, fatigued drivers are not dispatched, and every rider is belted.

Answer: A

The hazard is assessed and corrected, and restart is authorized: Correct. Stop Work Authority follows stop, assess, correct and then an authorized restart once the hazard (here, the combustibles) has been removed or controlled.

The welder decides alone when it feels safe to resume: Skips the joint assessment and authorized restart.

The crew signs a form accepting the fire risk: Accepting the risk on paper does not correct the hazard.

The job resumes once the welder's supervisor arrives: The supervisor arriving is not the same as the hazard being assessed and corrected.

Stop Work Authority: any worker may stop unsafe work without retaliation; the work is then assessed, corrected and restarted only with authorization.

Answer: A

Move away from the grinder and bond and ground both containers: Correct. Section 2 identifies a Category 2 flammable liquid, and Section 7 requires keeping it away from sparks and bonding and grounding during transfer; the grinder is an active ignition source.

Add a half-face respirator to his goggles and gloves: Section 8 relies on local exhaust and does not normally call for a respirator; this ignores the ignition hazard.

Relabel the safety can with the signal word Warning: Section 2 gives the signal word Danger, and relabeling does nothing about the sparks.

Warm the drum first so the liquid pours more easily: Section 7 says keep away from heat and store cool; warming increases vapor.

Read the document for what it says about the task: SDS sections, labels, manual warnings and permit conditions point directly to the hazard and the required control.

Answer: D

1. Write the formula: R = S × L × E.
2. Substitute the ratings: R = 5 × 3 × 2.
3. Compute: 5 × 3 = 15; 15 × 2 = 30.
4. Answer: R = 30. Check: all three factors are used and multiplied, so 30 is the score.

6: This is L × E = 3 × 2. The severity rating was left out.

10: This is S + L + E = 5 + 3 + 2. The ratings must be multiplied, not added.

15: This is S × L = 5 × 3. The exposure rating was left out.

30: Correct. R = 5 × 3 × 2 = 30.

Use every factor in the printed formula and multiply them; adding or dropping a factor gives a wrong score.

Answer: A

Reroute the pedestrian walkway behind fixed barriers away from the forklift aisle: Correct. Physically separating people from forklifts is an engineering control that removes the interaction at the corner. It does not depend on drivers or pedestrians seeing each other.

Mount a convex mirror at the corner: A mirror helps, but it still relies on drivers and pedestrians looking and reacting in time.

Remind forklift drivers to sound the horn at the corner: A horn rule is administrative. It depends on drivers remembering every time.

Require pedestrians to wear high-visibility vests: Vests are PPE. They do not help at a blind corner where no one can be seen.

Separation of people and mobile equipment beats mirrors, horn rules and vests.

Answer: A

Enclose the blower in a sound-absorbing enclosure: Correct. An enclosure is an engineering control that reduces noise at the source. 29 CFR 1910.95(b)(1) calls for feasible engineering or administrative controls above the permissible levels, with PPE when they fall short.

Require earmuffs for everyone working near the blower: Hearing protection is PPE. It is still needed until the noise is reduced, but it is not the first choice.

Post "Hearing Protection Required" signs around the blower: Signs are a warning (administrative) measure. They do not lower the noise level.

Limit how long each operator may work near the blower: Limiting time is an administrative control. It ranks below an engineering fix that lowers the noise for everyone.

Reduce noise at the source with engineering controls first; use time limits and hearing protection to cover what remains.

Answer: C

Acceptable, because the top reading is normal air: Testing only at the top misses gases that stratify lower in the space.

Hazardous, because the bottom LEL exceeds the setpoint: The LEL reading of 6% is below the 10% setpoint.

Hazardous, because oxygen at the bottom is below 19.5%: Correct. 19.1% O₂ is oxygen-deficient (below 19.5%), so the pit has a hazardous atmosphere at the bottom; entry waits for ventilation and retesting.

Acceptable, because CO and H₂S are below setpoints: Ignores the low-oxygen reading, which by itself makes the atmosphere hazardous.

Test at several levels and judge every gas: O₂ below 19.5% or above 23.5%, or flammables at 10% LEL or more, means a hazardous atmosphere.

Answer: B

No action, because the exposure is below 90 dBA: Confuses the 90-dBA PEL with the 85-dBA action level that triggers the program.

Include the operator in a hearing conservation program: Correct. 87 dBA is at or above the 85-dBA action level, so 29 CFR 1910.95(c) requires a hearing conservation program: audiometric testing, available hearing protectors, training and monitoring.

Remove the operator from the press until the level drops: Overreaction; the exposure is below the PEL and is managed through the hearing conservation program.

Install engineering controls before the operator may return: Feasible engineering or administrative controls are required above the 90-dBA PEL, not at 87 dBA.

OSHA noise: 85 dBA TWA action level triggers the hearing conservation program; 90 dBA TWA is the PEL that requires feasible controls.

Answer: B

The responder finishes the cleanup first and then reports the stick at the end of the shift: Delays the report; post-exposure evaluation and any prophylaxis are time-sensitive.

The responder washes the wound with soap and water and reports the exposure right away: Correct. An exposure incident is washed immediately and reported at once so the employer can start the confidential post-exposure medical evaluation and follow-up that 29 CFR 1910.1030(f)(3) requires.

The supervisor asks the injured worker who used the lancet whether they are infected: The supervisor is not to question or diagnose the source individual; testing and follow-up are handled through the medical evaluation.

The responder squeezes the wound and covers it, then waits to see if symptoms develop: Waiting for symptoms defeats the purpose of prompt post-exposure evaluation; the incident must be reported now.

For any needlestick or blood splash: wash or flush immediately, report immediately, and get the employee to the post-exposure medical evaluation.

Answer: C

Pull the worker free by the arm: The rescuer becomes a second victim while the circuit is live.

Start CPR while the worker is still in contact: No care can begin until the worker is clear of the energy source.

Open the disconnect to cut power to the motor: Correct. De-energize at the disconnect before anyone touches the victim; otherwise the rescuer becomes part of the circuit.

Call an electrician and wait for arrival: Wastes time when a known disconnect is close by; shut off first, then call for help.

For electrical contact: shut off the power (or move the victim with a nonconductive object if no shutoff is available), then call for help and give care.

Answer: B

1. 1. Formula: B = H / 4.
2. 2. Substitute: B = 16 ft / 4.
3. 3. Compute: B = 4.0 ft.
4. 4. Check: 4.0 ft out for 16 ft up is 1:4, so the base sits 4.0 ft from the wall.

3.2 ft: Divides by 5 instead of 4; the base is too close and the ladder is too steep, so it can tip backward.

4.0 ft: Correct. B = H/4 = 16 ft / 4 = 4.0 ft.

5.3 ft: Divides by 3; the base is too far out, so the ladder is too shallow and the feet can slide out.

64.0 ft: Uses the ratio backwards (multiplies by 4 instead of dividing).

The 1:4 rule sets the base out 1 ft for every 4 ft of height to the top support (manufacturer and reference-book practice).

Answer: D

Toxic gases, flammable gases, oxygen: Reverses the order; oxygen must come first because the combustible sensor needs adequate oxygen to read correctly.

Flammable gases, oxygen, toxic gases: Flammables before oxygen can give a falsely low combustible reading in an oxygen-deficient space.

Oxygen, toxic gases, flammable gases: Oxygen is first, but flammables come before toxics because a fire or explosion is the more immediate threat.

Oxygen, flammable gases, toxic gases: Correct. 1910.146 Appendix B: test oxygen first, then combustible gases and vapors, then toxic gases and vapors.

Test O₂ first, then flammables, then toxics.

Answer: C

3 ft: This is the depth of working space in front of electrical equipment (1910.303(g)), not an overhead-line clearance.

6 ft: Confuses the line clearance with a fall-protection height; it is less than the required distance.

10 ft: Correct. 29 CFR 1910.333(c)(3) requires unqualified persons, the equipment they use and vehicles to stay at least 10 ft from overhead lines rated 50 kV or less; 13.8 kV is within that range.

20 ft: This is a construction crane clearance (1926 Subpart CC), not the general-industry rule for unqualified workers near a line of 50 kV or less.

For overhead lines of 50 kV or less, unqualified workers and their conductive objects keep at least 10 ft away, plus 4 in for every 10 kV above 50 kV.