Free STSC Exam Flashcards

Falls, struck-by, caught-in/between, and electrocutions. They cause roughly 60% of construction worker deaths each year (BLS CFOI). Most of 29 CFR 1926 and OSHA's emphasis programs target these four, so they dominate the STSC.

Elimination, substitution, engineering controls, administrative controls, then PPE. Higher levels physically remove or reduce the hazard; PPE only protects the individual wearer and depends on correct use, so it is the last resort.

PPE does not remove the hazard. It only reduces exposure for one worker and fails if it is the wrong type, worn incorrectly, damaged, or removed. Engineering controls protect everyone in the area regardless of behavior.

Struck-by means a moving object strikes the worker (falling tool, swinging load, vehicle). Caught-in/between means the worker is crushed, pinched, or compressed between objects or by collapsing material, such as a trench cave-in or being pinned by equipment.

The right and duty of any worker to halt a task when an imminent or uncontrolled hazard appears, without fear of reprisal. It shifts safety from a supervisor-only decision to a shared responsibility and is a hallmark of a strong safety culture.

Under 29 CFR 1926.501, workers on a walking/working surface with an unprotected edge 6 feet or more above a lower level must use guardrails, safety nets, or a personal fall arrest system. (General industry under 1910 uses 4 feet.)

42 inches plus or minus 3 inches (39 to 45 inches) above the surface, per 1926.502(b). The top rail must withstand 200 pounds of outward or downward force, and a midrail sits at about half that height.

Anchorage, Body harness (full-body), and Connecting device (shock-absorbing lanyard or self-retracting lifeline). Body belts have been prohibited for fall arrest since 1998 because they concentrate arrest forces on the abdomen.

5,000 pounds per attached worker, unless the anchorage is engineered as part of a complete system with a safety factor of at least two under a qualified person's supervision (1926.502(d)(15)).

Scaffolds fall under Subpart L (1926.451(g)), which sets the fall protection threshold at more than 10 feet, not the 6-foot general trigger. Knowing that scaffolds, steel erection, and general work each have different triggers is a common STSC trap.

A personal fall arrest system must limit free fall to 6 feet or less and stop the worker before contacting a lower level. It must also limit arresting force on the body to 1,800 pounds when used with a full-body harness.

A bounded area where certain work (like leading-edge or overhand bricklaying) may proceed without conventional fall protection, entered only by authorized workers. It is paired with a safety monitoring system as an alternative measure, not a default.

Gaps between planks and between the platform and uprights must be no more than 1 inch, per 1926.451(b). Wider gaps (up to 9.5 inches) are allowed only where the configuration cannot be fully planked. Platforms must also be fully decked.

A competent person, before each work shift and after any event that could affect structural integrity (1926.451(f)(3)). A competent person can both identify hazards and is authorized to take prompt corrective action.

When a supported scaffold's height exceeds 4 times its minimum base width, it must be restrained from tipping by guying, tying, or bracing. Tip-over from excessive height-to-base ratio is a leading scaffold fatality cause.

At least 3 feet above the upper landing surface (1926.1053(b)(1)). If it cannot extend 3 feet, secure the top and provide a grab rail. This gives a worker something to hold while stepping off.

A portable straight or extension ladder should be set so its base is 1 foot out from the wall for every 4 feet of working height (a 75-degree angle). Too steep risks tipping backward; too shallow risks the base sliding out.

Cross-braces are diagonal and not designed as a climbing surface, so 1926.451(e) prohibits using them for access. Workers must use a ladder, stair tower, ramp, or integral prefabricated access when the platform is more than 2 feet above the access point.

Type A (most stable cohesive soil, e.g., clay), Type B (moderately stable), and Type C (least stable, e.g., gravel, sand, or submerged soil). Classification determines the allowable sloping angle and protective system.

Type A slopes at 3/4:1 (about 53 degrees), Type B at 1:1 (45 degrees), and Type C at 1.5:1 (about 34 degrees). Less stable soil requires a flatter, wider cut to prevent cave-in.

At 5 feet deep or more, unless the excavation is entirely in stable rock. Below 5 feet a competent person may waive it only if the soil shows no potential for cave-in. At 20 feet or deeper the system must be engineered.

Excavated soil, materials, and equipment must be kept at least 2 feet from the trench edge (1926.651(j)). This prevents material from rolling back in and reduces surcharge load that can trigger a wall collapse.

A ladder, ramp, stairway, or other safe means of exit must be within 25 feet of lateral travel for every worker (1926.651(c)). This lets workers escape quickly if the trench begins to fail.

Sloping/benching cuts the walls back to a safe angle. Shoring (e.g., hydraulic) braces the walls in place. Shielding (a trench box) does not stop a cave-in but protects workers inside it. All three are accepted protective systems.

A competent person inspects the excavation, adjacent areas, and protective systems daily and as conditions change (rain, vibration, added load). If hazardous conditions are found, workers are removed until corrected.

A Ground-Fault Circuit Interrupter cuts power within milliseconds when current leaks to ground. Under 1926.404, all 120V single-phase 15- and 20-amp receptacles on a construction site must have GFCI protection, or an Assured Equipment Grounding Conductor Program must be used instead.

A breaker protects equipment and wiring from overload and short circuits (high current). A GFCI protects people from electrocution by tripping on small ground-fault current (as little as 5 milliamps). They guard against different failures and are not interchangeable.

LOTO isolates and de-energizes a machine or circuit, then locks the energy-isolating device so it cannot be re-energized while workers service it. It controls hazardous energy, electrical, hydraulic, pneumatic, mechanical, thermal, and gravity, not just electricity.

A lock physically prevents the device from being operated; a tag only warns. A tag alone is allowed only when a device cannot accept a lock, and it must give protection equivalent to a lock. Locks are always the preferred, more reliable control.

Equipment and unqualified workers must stay clear of energized overhead lines, generally at least 10 feet for lines up to 50 kV, with greater clearance for higher voltage. Contact with overhead lines is a leading electrocution cause for crane and aerial-lift work.

An alternative to GFCIs in which a competent person inspects and tests all cord sets, receptacles, and plug-connected equipment on a set schedule, recording results. It verifies the equipment grounding path is intact so a fault returns safely to ground.

Under 1926.1153, the PEL for respirable crystalline silica is 50 micrograms per cubic meter as an 8-hour TWA, with an action level of 25. Silica dust from cutting concrete, brick, or stone causes silicosis, lung cancer, and kidney disease.

Table 1 lists specified construction tasks with matched engineering controls (water/wet methods or vacuum dust collection) and respirator requirements. Following Table 1 fully lets an employer skip individual air monitoring for that task.

A Permissible Exposure Limit is the maximum legal airborne concentration of a substance a worker may be exposed to, usually as an 8-hour time-weighted average. Exceeding it triggers controls, monitoring, and sometimes medical surveillance.

The action level is a lower concentration (often half the PEL) that triggers requirements like exposure monitoring, training, and medical surveillance, before the legal limit is reached. It is an early-warning threshold designed to keep exposures from climbing to the PEL.

When the 8-hour time-weighted average noise exposure reaches 85 dBA (the action level), employers must provide audiometric testing, hearing protection, and training. Feasible engineering or administrative controls are required when exposure exceeds 90 dBA.

Heat exhaustion brings heavy sweating, weakness, and nausea, and is treated with rest, shade, and fluids. Heat stroke is a medical emergency: hot dry skin or confusion, high body temperature, and possible collapse. Call 911 and cool the worker immediately; it can be fatal.

A test (qualitative or quantitative) confirming a tight-fitting respirator seals to a specific worker's face. It is required before first use and at least annually. Facial hair at the seal makes a fit test fail, so a respirator cannot be relied upon.

A confined space, limited entry/exit and not designed for continuous occupancy, that also has at least one of: hazardous atmosphere, engulfment potential, an inwardly converging shape, or any other serious hazard. Construction confined space is covered by 1926 Subpart AA.

About 19.5% to 23.5% oxygen. Below 19.5% is oxygen-deficient; above 23.5% is oxygen-enriched and dangerously raises fire risk. Atmosphere must be tested before and during entry in the order: oxygen, then flammables, then toxics.

An authorization, required before welding, cutting, grinding, or other spark-producing work, that confirms the area is cleared of combustibles, a fire watch is posted, and extinguishers are ready. The fire watch typically stays for at least 30 minutes after work ends.

Pull the pin, Aim at the base of the fire, Squeeze the handle, and Sweep side to side. Aiming at the flames instead of the fuel base wastes the agent. Use an extinguisher only on a small, contained fire with a clear escape path behind you.

Procedures for reporting emergencies, evacuation routes and exits, accounting for all personnel after evacuation, rescue and medical duties, and an alarm system. On a changing construction site, routes and muster points must be updated as the work progresses.

A qualified rigger selects and inspects slings and hardware, determines load weight and center of gravity, and rigs the load so it lifts level and secure. Rigging must be inspected before each shift; damaged slings are removed from service immediately.

The rotating superstructure (counterweight and boom) can crush a worker against a fixed object, a caught-between hazard. The swing radius must be barricaded so no one can enter the area where the crane body rotates.

A method that breaks a task into steps, identifies the hazard in each step, and defines a control for it before work starts. In construction it is often called an AHA (Activity Hazard Analysis) and is reviewed with the crew during the pre-task briefing.

It finds the underlying system failures (training gaps, missing guards, poor procedures) rather than blaming the worker. Asking 'why' repeatedly past the immediate cause prevents recurrence; stopping at 'employee error' leaves the real hazard in place.

Work-related injuries and illnesses beyond first aid: any death, days away from work, restricted duty or job transfer, medical treatment beyond first aid, or loss of consciousness. Simple first-aid cases are not recordable.

Lagging indicators measure failures after the fact (injury rates, lost-time incidents). Leading indicators are proactive measures (inspections completed, near-miss reports, training hours) that predict and prevent incidents. Strong programs track both.

Short, frequent, jobsite-specific safety briefings reinforce hazard awareness for the day's actual tasks and conditions, give workers a chance to raise concerns, and build engagement. Consistency and crew participation matter more than length.