NIOSH SHO Hazard Control common mistakes
NIOSH SHO Hazard Control · Understand the traps and how to avoid them.
When asked to anticipate hazards for a task or process, the candidate lists only the obvious chemical or physical agent named in the prompt and omits the co-exposures and by-products the same operation creates (e.g., welding fumes plus UV radiation, ozone, noise, and heat).
Candidates treat hazard identification as naming the headline agent rather than systematically walking the work through agent families (chemical, physical, biological, ergonomic, safety) and the process steps that generate each. This is the single most common cause of lost points in anticipation questions, because graders award credit for breadth of correctly attributed agents.
What to do instead
Before answering, run a fixed checklist over the task: raw materials, intermediates, products, by-products, energy sources (noise, heat, radiation, pressure), physical hazards (pinch, fall, electrical), ergonomic stressors, and biological agents. For each process step, ask what enters, what leaves, and what energy is released. Write the resulting list out explicitly rather than summarizing it in prose.
The candidate selects a control based on how familiar or easy it is (respirators, gloves, training) instead of ranking options against the hierarchy, so a substitution or engineering control that would work is never considered.
PPE and training are the controls most workers and supervisors actually see in place, so they come to mind first. Under time pressure, candidates write the first plausible control rather than deliberately generating options at each level of the hierarchy before choosing.
What to do instead
Answer in two explicit steps: first list at least one candidate control at each hierarchy level (elimination, substitution, engineering, administrative, PPE), then justify the selection by effectiveness, reliability, and feasibility. If PPE is the final answer, state which higher-level options were considered and why they were rejected.
The candidate treats the hierarchy as a strict legal ranking and declares that a lower-level control is never acceptable, rather than explaining that the hierarchy is a preference order applied with feasibility, and that residual risk after higher controls must still be managed.
Simplified training materials present the hierarchy as an absolute rule, so candidates over-apply it and miss questions that ask about combined controls, interim controls during an engineering change, or situations where a lower control is the only feasible option.
What to do instead
Frame the hierarchy as a preference order: prefer higher levels, document why a higher level is not feasible, and always describe the combination of controls needed to bring residual risk to an acceptable level. Practice wording answers that combine an engineering control with administrative and PPE backup.
When asked to evaluate a ventilation control, the candidate accepts 'local exhaust ventilation is installed' as the answer and never addresses capture velocity, hood placement relative to the source, or whether the contaminant is being drawn away from the breathing zone.
Candidates conflate the presence of equipment with effective control. Questions about ventilation effectiveness are usually testing whether the candidate knows that a hood in the wrong position or with inadequate capture velocity provides little protection, even though it is 'installed.'
What to do instead
For any LEV question, address four points: source capture at the point of generation, capture velocity appropriate to the contaminant, hood orientation so the contaminant is pulled away from the worker's breathing zone, and make-up air so the system actually exhausts. State that installation alone is not verification.
The candidate recommends dilution ventilation for a highly toxic or low-occupational-exposure-limit contaminant, or for a contaminant with poor warning properties, instead of recognizing that dilution is suited only to low-toxicity contaminants generated at a steady, known rate.
Dilution ventilation is cheap and simple, so it appears in answers as a generic 'ventilation' fix. Candidates do not connect the choice to contaminant toxicity, generation rate variability, or the need for reliable warning properties.
What to do instead
Memorize the boundary: dilution ventilation is appropriate for low-toxicity contaminants with relatively uniform generation rates and adequate warning properties; it is not appropriate for highly toxic agents, intermittent high releases, or confined spaces. When a question names a carcinogen or a substance with a very low exposure limit, default to source capture or substitution.
The candidate proposes administrative controls such as job rotation, training, or scheduling as the primary fix for a hazard that could be engineered out, and does not acknowledge that administrative controls depend on consistent human performance and are therefore less reliable.
Administrative controls are inexpensive and quick to write, so they dominate answers. Candidates also underweight the reliability argument: a control that requires every worker to do the right thing every shift fails more often than a physical barrier.
What to do instead
When proposing an administrative control, state explicitly that it is a supplement, name the engineering or substitution option it backs up, and explain how compliance will be verified (supervision, audits, exposure monitoring). Reserve administrative controls as primary only when higher-level controls are demonstrably infeasible.
The candidate answers a PPE question by naming the equipment (e.g., 'a respirator' or 'nitrile gloves') without specifying the selection basis: assigned protection factor and cartridge or filter class for respirators, or chemical resistance and breakthrough time for gloves.
Candidates memorize equipment names but not selection criteria. Exam questions about PPE almost always hinge on matching the device to the hazard, the exposure concentration, and the task duration, not on naming a product category.
What to do instead
For every PPE answer, state the hazard, the required protection level, the specific device class, and the basis for the match. For respirators, tie the choice to the exposure concentration relative to the occupational exposure limit and the assigned protection factor. For gloves, tie the choice to the chemical, permeation and breakthrough data, and task duration.
The candidate describes a PPE program as issuing equipment and training workers, omitting fit testing, medical evaluation, respirator maintenance and storage, and program evaluation by a qualified administrator.
The written-program elements of a respiratory protection program are numerous and easy to compress into 'train and fit.' Candidates who have not worked through the regulatory program requirements answer at the level of the device rather than the program.
What to do instead
Keep a memorized program checklist: written procedures, hazard assessment and selection, medical evaluation, fit testing, training, maintenance and storage, breathing-air quality where applicable, and periodic program evaluation. When a question asks about a PPE program, walk the checklist and address the elements the scenario implicates.
The candidate treats an initial exposure assessment or a single air sample as proof that a control works, without describing periodic reassessment, change-triggered reassessment, or comparison against the occupational exposure limit with appropriate statistics.
Candidates conflate 'we measured it once' with verification. Verification questions test whether the candidate understands that controls degrade, processes change, and a single sample does not characterize exposure variability.
What to do instead
For verification answers, specify the method, the sampling strategy (representative worst-case, multiple workers and shifts), the comparison basis (exposure limit and averaging time), the reassessment interval, and the triggers for reassessment such as process change, new chemicals, or control modification. State that the result must be documented and communicated.
The candidate answers a monitoring or program-evaluation question with a general statement that the program 'should be reviewed regularly' without specifying indicators, responsible parties, recordkeeping, or how findings feed back into control selection.
Program evaluation is the least concrete domain, so candidates fall back on vague assurance language. Graders look for measurable indicators and a feedback loop, and generic statements earn little credit.
What to do instead
Name concrete evaluation inputs: exposure monitoring results against limits, control inspection and maintenance records, near-miss and incident data, worker symptom and feedback reports, training completion, and audit findings. Then describe the feedback loop: who reviews, at what interval, and how findings trigger reassessment of hazards and controls.