STSC Hazard Recognition and Risk Assessment 2 — Questions and Answers
Question 1: In construction risk assessment, what does the term 'residual risk' mean?
- The risk that existed before any controls were applied
- The risk that remains after all feasible controls have been implemented (Correct answer)
- The risk associated only with chemical hazards on site
- The financial risk of a construction project
Correct answer: The risk that remains after all feasible controls have been implemented
Residual risk is the level of risk that remains after all practical hazard controls have been applied. It helps determine whether additional measures or PPE are still needed.
After applying elimination, substitution, engineering controls, and administrative controls, some degree of risk may still remain — this is residual risk. Safety managers must evaluate residual risk to determine if it is acceptable or if additional controls (such as PPE) are needed. If residual risk remains unacceptably high, more effective controls must be found. Understanding residual risk is essential for STSC supervisors when reviewing JHAs and approving work permits for high-hazard tasks.
Question 2: Which of the following is an example of an 'engineering control' used to reduce hazards on a construction site?
- Requiring workers to wear hard hats
- Posting warning signs near floor openings
- Installing guardrails around an elevated work platform (Correct answer)
- Conducting daily safety briefings before work begins
Correct answer: Installing guardrails around an elevated work platform
Engineering controls physically change the work environment or equipment to reduce hazard exposure — guardrails eliminate the fall hazard rather than just protecting a worker from its consequences.
Engineering controls are physical modifications to the workplace, equipment, or processes that remove or reduce hazard exposure without relying on worker behavior. Examples include: guardrails and barriers, machine guarding, local exhaust ventilation, interlocks, and noise-dampening enclosures. In contrast, administrative controls (such as safety briefings or job rotation) and PPE (such as hard hats) rely on human behavior and are considered less effective. Engineering controls rank third in the hierarchy of controls, after elimination and substitution.
Question 3: A safety supervisor notices workers are repeatedly bypassing a machine guard. What is the MOST effective long-term solution?
- Issue verbal warnings and document the behavior
- Investigate why workers bypass the guard and redesign it to be user-friendly without compromising protection (Correct answer)
- Increase the frequency of safety inspections
- Require workers to sign a form acknowledging the guard must remain in place
Correct answer: Investigate why workers bypass the guard and redesign it to be user-friendly without compromising protection
Repeatedly bypassed guards often indicate a design problem. Investigating the root cause and redesigning the guard addresses the underlying issue rather than enforcing compliance against a poorly designed system.
When workers consistently bypass a safety control, it often signals that the control interferes with the work, is uncomfortable, or is poorly designed. The most effective solution is to identify why the guard is being bypassed — perhaps it blocks vision, impedes the workflow, or vibrates loose — and redesign it to eliminate those issues without compromising protection. Simply increasing enforcement or documentation addresses symptoms without fixing the root cause, which is an ineffective long-term strategy and a hallmark of a reactive rather than proactive safety culture.
Question 4: Under OSHA 29 CFR 1926, which of the following activities requires a written permit before work can begin?
- Painting exterior walls
- Cutting concrete with a walk-behind saw
- Entry into a permit-required confined space (Correct answer)
- Operating a forklift on a level surface
Correct answer: Entry into a permit-required confined space
29 CFR 1926.1203 requires a written entry permit for entry into permit-required confined spaces, which have serious hazards such as atmospheric dangers, engulfment risks, or configuration hazards.
A permit-required confined space is one that has or has the potential for a hazardous atmosphere, material that can engulf an entrant, internal configuration that could trap an entrant, or any other recognized serious safety or health hazard. OSHA 29 CFR 1926.1203 requires employers to issue a written entry permit before entry into such spaces. The permit specifies authorized entrants, attendants, entry supervisors, known hazards, atmospheric test results, required equipment, and rescue procedures. This formal permit system is one of the most important hazard control mechanisms in construction.
Question 5: What is the significance of the 'Fatal Four' in OSHA's construction industry focus?
- The four most common OSHA citations issued to construction employers
- The four leading causes of worker deaths in construction: falls, struck-by, caught-in/between, and electrocution (Correct answer)
- The four types of PPE most frequently found defective during inspections
- The four OSHA standards most frequently violated on multi-employer worksites
Correct answer: The four leading causes of worker deaths in construction: falls, struck-by, caught-in/between, and electrocution
OSHA's 'Fatal Four' refers to the four leading causes of construction fatalities: falls, struck-by objects, caught-in/between hazards, and electrocution — which together account for the majority of construction worker deaths.
OSHA's Fatal Four — falls, struck-by, caught-in/between, and electrocution — consistently account for more than half of all construction worker deaths each year. Falls are the leading cause, followed by struck-by objects (often from falling materials or vehicles), caught-in/between hazards (such as unguarded machinery or cave-ins), and electrocution (often from contact with overhead power lines or unguarded electrical systems). STSC-certified supervisors are expected to recognize, assess, and control all four categories of hazards as a primary safety responsibility.
Question 6: When assessing the severity of a potential hazard, what two factors are typically combined to produce a risk rating?
- Cost of control and number of workers affected
- Probability of occurrence and severity of potential harm (Correct answer)
- Frequency of work activity and worker experience level
- Regulatory citation history and insurance premium impact
Correct answer: Probability of occurrence and severity of potential harm
Risk is typically assessed by combining the probability (likelihood) that the hazard will cause harm with the severity (consequence) of the potential injury or illness, producing a risk matrix rating.
A standard risk matrix combines two dimensions: (1) Probability — how likely is it that the hazard will cause an incident (often rated from rare to almost certain); and (2) Severity — how serious would the resulting injury or illness be (often rated from minor first aid to catastrophic/fatal). Multiplying or combining these scores produces a risk rating (low, medium, high, or critical) that guides prioritization of hazard controls. High probability x high severity hazards require immediate action; low probability x low severity hazards may be managed with routine controls.
STSC Hazard Recognition and Risk Assessment 2
In construction risk assessment, what does the term 'residual risk' mean?