OHST common mistakes
OHST · Understand the traps and how to avoid them.
Choosing injury rate metrics such as TRIR or DART when the question asks for a proactive measure of safety and health program effectiveness.
These are the numbers candidates see most often in workplace reports, so they feel like the default measure of program success.
What to do instead
Classify metrics before answering: leading indicators include inspection completion, near-miss reporting, audit closure, training completion, and employee participation; lagging indicators include injury and illness rates. For any question asking about prevention, progress, or program health, select the leading indicator.
Ending an incident investigation at the immediate cause, such as 'employee failed to follow procedure,' and selecting retraining or discipline as the corrective action.
The visible unsafe act is easy to identify, and disciplinary language appears in many workplace procedures and distractors.
What to do instead
Use a causal chain: identify direct cause, contributing causes, and root cause. Treat 'employee error' as a starting point, then examine training adequacy, procedure usability, supervision, equipment design, and management-system factors. Choose corrective actions that remove or control the systemic cause rather than only addressing the individual.
Treating PEL, REL, and TLV as interchangeable, or comparing a short-term sample directly to an 8-hour TWA without checking the averaging period.
The numbers are memorized as a single value without the legal and technical conditions attached to each limit.
What to do instead
For every exposure limit, identify the source and averaging basis: OSHA PEL is enforceable, NIOSH REL and ACGIH TLV are recommendations; 8-hour TWA, 15-minute STEL, and ceiling limits are not interchangeable. Match the sample duration to the limit before comparing results, and use mixture formulas when multiple substances act on the same target organ.
Selecting an air-sampling or direct-reading method without confirming that it is validated for the contaminant and then sampling only a convenient location or time.
A monitor or colorimetric tube appears to give a definitive answer, and convenience often drives where the sample is taken.
What to do instead
Use the recognized sampling and analytical method for the specific contaminant, such as charcoal tubes for many organic vapors and filters for metals or particulates. Sample in the breathing zone, during representative worst-case conditions, for the required duration, and include field blanks and laboratory analysis as applicable. Do not rely on colorimetric tubes with known cross-sensitivity for quantitative compliance decisions.
Selecting personal protective equipment as the primary control whenever a hazard is identified.
PPE is visible, familiar, and often easier to purchase than redesigning a process or installing engineering controls.
What to do instead
Apply the hierarchy of controls in order: elimination, substitution, engineering controls, administrative controls, and PPE. When a question asks for the best or most effective control, choose the highest feasible level that addresses the hazard source, and treat PPE as the last line of defense or a temporary measure.
Calling a task 'high risk' merely because it involves a recognized hazard, without assessing severity, likelihood, and exposure.
Hazard and risk are used interchangeably in everyday workplace language, so candidates skip the probability and consequence analysis.
What to do instead
Define hazard as the source of potential harm and risk as the combination of likelihood and severity given actual exposure. Before choosing controls or ranking priorities, assign severity and probability, consider frequency and duration of exposure, and use the resulting risk level to decide whether the task is acceptable or requires additional controls.
Assuming lockout/tagout applies only to electrical energy, or treating a tag alone as equivalent to a lock in every situation.
LOTO is often learned through electrical maintenance examples, and tagout appears simpler when locks are inconvenient.
What to do instead
Apply energy isolation to all hazardous energy sources, including mechanical, hydraulic, pneumatic, thermal, chemical, and gravity. Use lockout as the primary method; use tagout alone only when lockout is infeasible and the employer can demonstrate equivalent protection. Verify isolation by attempting startup or testing for zero energy before work begins.
Choosing a fire extinguisher by convenience rather than by fire class, or directing employees to use portable extinguishers on a fire beyond incipient stage.
Extinguisher labels and class letters are memorized as symbols without a clear mapping to fuel type and fire size.
What to do instead
Match the extinguisher to the fuel: Class A for ordinary combustibles, B for flammable liquids and gases, C for energized electrical equipment, D for combustible metals, and K for cooking oils and fats. Portable extinguishers are for incipient-stage fires only and only by trained employees; for growth-stage or large fires, activate the alarm and evacuate.
Treating the emergency action plan as a set of evacuation route maps and missing required elements such as alarm signals, reporting procedures, accounting for personnel, rescue duties, and drills.
Floor plans are the most visible part of emergency planning, so they dominate the candidate's mental model of an EAP.
What to do instead
Memorize the EAP elements: preferred and alternate evacuation routes, procedures for employees who remain to perform critical operations, accounting for all employees after evacuation, rescue and medical duties, reporting procedures, alarm systems, and training and drill requirements. Distinguish evacuation from shelter-in-place and select the response that matches the emergency scenario.
Deciding whether a waste is hazardous by reading the container label or assuming that any industrial waste is hazardous, instead of applying the RCRA listing or characteristic determination.
Everyday labels such as 'hazardous' or 'chemical waste' blur the difference between a product hazard and a regulatory waste classification.
What to do instead
Make the waste determination using RCRA criteria: determine whether the waste is a listed hazardous waste (F, K, P, or U lists) or exhibits a characteristic of ignitability, corrosivity, reactivity, or toxicity. Then calculate generator status from the quantity generated per month, and keep the determination documentation.