OSHA Scaffold Safety Quiz — 29 CFR 1926.450-454 Practice Questions — Page 3 of 4
Free OSHA 30-Hour Construction scaffold safety practice test with 40 realistic scenarios. Covers supported scaffolds, suspended scaffolds, aerial lifts, platform construction, guardrails, and competent person inspection with 29 CFR 1926 Subpart L references. (Page 3 of 4)
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Q21/ 40
A plastering crew is working on a multi-point suspended scaffold 60 feet long, suspended by 4 wire ropes. The scaffold is rated for 50 psf (medium duty). During plastering, workers accumulate approximately 400 lbs of wet plaster debris on the platform plus 3 workers (250 lbs each = 750 lbs). The platform is 5 feet wide. What is the load per square foot?
✅ Correct Answer: B
1926.451(a)(6): scaffolds must not be loaded in excess of the maximum intended load. While the average 3.8 psf is below 50 psf, a 60-foot multi-point suspended scaffold must consider concentrated loads between suspension points. 1926.451(d)(9): suspension ropes on adjustable suspension scaffolds shall be of sufficient length to allow the platform to be lowered to the ground. 1926.451(a)(3): platforms must not deflect more than 1/60 of the span. A 60-foot long platform between 4 points (3 spans of ~20 feet each) must be engineered for the load distribution. The issue is structural adequacy of the platform spanning between suspension points, not just the average load.
Q22/ 40
A scaffold erector is installing a pump jack scaffold (for siding work) on a two-story house. The pump jack poles are 2×4 lumber, 28 feet long, spliced at mid-height using a metal sleeve. Each pump jack bracket supports one worker and tools. What are the key requirements for this setup?
✅ Correct Answer: B
1926.452(j)(3): pump jack scaffolds shall have poles made of straight-grained lumber, free of knots that would impair strength. The poles must be adequately braced and the splices must develop the full strength of the member. 1926.452(j)(6): the maximum height of a pump jack scaffold is 30 feet. 1926.452(j)(5): brackets must be two-point suspension type. Standard 2×4 lumber used as poles must be No. 1 or select structural grade — common construction-grade 2×4s may contain knots and defects that compromise the pole's bending strength.
Q23/ 40
A scaffold built next to a highway overpass has 2×10 wood planks for the platform. One plank has a large knot (about 3 inches in diameter) in the middle of the span. The plank is otherwise sound. The competent person says it's fine. What does 1926.451 require regarding scaffold planking?
✅ Correct Answer: B
1926.451(a)(1): scaffold planking must be capable of supporting the intended load. 1926.451(a)(7): scaffold planking shall be scaffold grade as recognized by grading rules. Appendix A to Subpart L specifies that scaffold grade lumber must be certified by a grading agency and marked. A 3-inch knot in the middle of a span creates a stress concentration — under load, the plank is most likely to fail at the knot. The knot acts as a natural fracture point, significantly reducing the bending strength of the plank. Scaffold grade lumber specifically limits knot size relative to the cross-section.
Q24/ 40
Workers on a 40-foot high supported scaffold are using a nylon debris net draped over the scaffold's exterior to contain falling tools. The net is attached to the guardrails with zip ties. A 2-lb hammer slips through a gap between the net and the scaffold platform. What is the correct falling object protection requirement?
✅ Correct Answer: B
1926.451(h)(1): toeboards shall be installed on all open sides and ends of scaffolds more than 10 feet above lower levels, unless employees below are protected by barricades or other means. 1926.451(h)(2): where tools or materials may fall, additional protection such as screens or panels extending from toeboard to top rail OR a debris net shall be provided. Zip ties are not a structural attachment — debris nets must be securely fastened with adequate strength connections. Gaps between the net and platform defeat the purpose.
Q25/ 40
A tube and coupler scaffold is being erected. The qualified person's design specifies certain tube diameters and coupler types. The erector runs out of right-angle couplers and substitutes swivel couplers with the same load rating. Is this acceptable?
✅ Correct Answer: B
1926.451(a)(6): scaffolds shall be designed by a qualified person. 1926.451(d)(1): scaffold components shall be used in accordance with the manufacturer's recommendations. Swivel couplers have different load-transfer characteristics than right-angle (double) couplers — they allow rotation and may not maintain the same rigidity at connections. The qualified person's design assumes specific coupler types at each connection point. Substituting without re-engineering changes the structural behavior of the scaffold system. Swivel couplers are intended for diagonal bracing, not primary load-bearing connections.
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Q26/ 40
A scaffold is built partially over an unmarked underground vault. One base plate settles 3 inches into the ground after a rain, causing the scaffold to tilt. The competent person had checked the ground condition the day before (dry weather). What should have been done differently?
✅ Correct Answer: B
1926.451(c)(2): scaffold footings shall be level and capable of supporting the loaded scaffold without settling or displacement. 1926.451(f)(3): scaffolds shall be inspected before each work shift and after any occurrence that could affect structural integrity. A competent person should anticipate that rain will saturate soil over a vault (which has a void underneath), causing settlement. Mud sills, timber mats, or concrete pads should have been used to distribute the load. After the rain, the scaffold should have been re-inspected and relevelled before use.
Q27/ 40
On a shipyard scaffold, workers are welding on a tank interior. The scaffold is made of steel tube and coupler. A welding lead (cable) is draped over the scaffold frame — the insulation on the cable is worn, exposing bare copper at a point where it contacts the scaffold tube. What is the hazard?
✅ Correct Answer: B
1926.451(f)(13): welding can only be performed on scaffold components after a qualified person approves the procedure. The real hazard is electrical: a damaged welding lead contacting the steel scaffold frame energizes the entire scaffold at welding voltage (typically 60-80V DC open circuit, but AC systems can be 80V+). All workers on the scaffold become part of the circuit if they touch the frame and any grounded object. The welding lead must be insulated, routed away from the frame, and inspected before use. 1926.351(c) requires welding cables to be free from repairs or splices within 10 feet of the electrode holder unless spliced with insulated connectors of capacity equal to the cable.
Q28/ 40
A scaffold platform consists of two 2×10 planks laid side-by-side over a 7-foot span. The planks are not secured (no cleats, no wire ties). Under load, one plank shifts sideways, creating a gap, and a worker's foot slips through. What does 1926.451 require regarding plank securing?
✅ Correct Answer: A
1926.451(a)(12): scaffold planks shall be secured against displacement. 1926.451(b)(6): on supported scaffolds, planks must overhang the end supports between 6 and 12 inches unless secured to prevent movement. The planks must also be cleated or otherwise secured to prevent lateral movement. Two unsecured planks side-by-side can shift independently, creating dangerous gaps. Cleats (wood blocks attached to the underside that hook against the support), wire ties, or manufactured hook planks prevent this. This is one of the most common scaffold violations.
Q29/ 40
A competent person is performing a pre-shift scaffold inspection and notices that a cross-brace on a frame scaffold is missing its locking pin — the brace is held in place by gravity. Workers are about to start their shift. What is the competent person's immediate duty?
✅ Correct Answer: B
1926.451(f)(3): scaffolds shall be inspected by a competent person before each work shift. 1926.451(f)(4): any part of a scaffold damaged or weakened shall be immediately repaired or replaced. Cross-braces are structural members — without the locking pin, the brace can disengage from the frame, causing the scaffold frame to lose lateral stability and potentially collapse. The competent person has the authority to stop work and must exercise it. Simply warning workers is insufficient — the scaffold must be physically prevented from use until the hazard is corrected.
Q30/ 40
A window washing crew is using a two-point suspension scaffold at the 25th floor. The scaffold has two independent suspension ropes, each with a fall arrest system attached to separate vertical lifelines. One of the two suspension ropes shows 3 broken wires in one lay length. The crew says they'll fix it after today's work. What must happen?
✅ Correct Answer: B
1926.451(d)(10): wire rope used for scaffold suspension shall be inspected before each workshift. 1926.451(f)(4): any damaged or weakened component shall be immediately repaired or replaced. Wire rope inspection criteria under 1926.1414 (applicable by reference) say that 3 broken wires in one lay length requires replacement. The fact that there are two suspension ropes does not justify continuing with a damaged rope — the system is designed assuming both ropes are intact. A rope failure could cause the platform to tilt, ejecting workers even if the fall arrest system catches them.