Good to Know — Rules of Thumb (Safety / HSE)
Field-tested approximations and sanity checks for safety, industrial hygiene, and environmental professionals. Estimates for reasonableness checks — compliance follows the regulation, the consensus standard, and the site's data.
Incident metrics
- TRIR/DART: (cases × 200,000)/hours. 200,000 = 100 workers × 2,000 h. Below ~1.0 is world-class in heavy industry; above the industry average demands explanation, not excuses.
- The triangle: for every serious injury there are ~tens of minor injuries and ~hundreds of near misses (the Heinrich/Bird ratios are dated in detail but the shape holds) — the near-miss rate is the leading indicator worth managing.
- Cost: uninsured incident costs run ~4–10× the insured (the iceberg). A $50k comp claim is a $200–500k event to the business — the language that unlocks prevention budgets.
Industrial hygiene
- OEL hierarchy: PEL = legal floor (often 1970s-era); TLV = consensus best practice (usually more protective); REL = NIOSH recommendation. Design to the TLV; comply with the PEL; never confuse them.
- TWA: Σ(C·T)/8. If the arithmetic mean is 40% of the OEL but the GSD is 2.5, the 95th percentile is ~1.8× the OEL — compliance lives in the tail, not the mean.
- Mixtures: Σ(C/OEL) ≤ 1 for same-target-organ effects. Each-below-the-limit ≠ compliant.
- Breakthrough: back section >10% of front = invalid sample. Non-negotiable.
- Noise: OSHA 90 dBA/5-dB; NIOSH-ACGIH 85 dBA/3-dB. 85 dBA = hearing-conservation trigger under OSHA. Halving the dose takes 5 dB (OSHA) or 3 dB (NIOSH) — know which the question uses.
- Ventilation: Q = GK/C for dilution (and dilution is rarely the answer for toxics — LEV is). Capture velocity 100–500 fpm by release energy; transport velocity 2,000–4,500 fpm by contaminant; make-up air is the commissioning step everyone forgets.
- Respirators: APFs — half-face 10, full-face 50, PAPR 25–1,000, SCBA 10,000. MUC = APF × OEL. No fit test, no protection (and no facial hair at the seal — the exam and the inspector agree).
- Heat: WBGT + work/rest per ACGIH TLV; acclimatization takes 7–14 days. Water-rest-shade is the program, not the poster.
Safety engineering
- Hierarchy of controls: elimination → substitution → engineering → administrative → PPE. Any proposal that starts at PPE is upside down.
- Fall clearance: free fall + deceleration + stretch + margin. A 6-ft lanyard on a 10-ft anchor doesn't clear a 12-ft fall — do the math before the worker does it empirically.
- Machine guarding: the point of operation must be guarded where exposure exists — "the operator is experienced" is not a guard.
- LOTO: 1910.147 — energy isolation, lock, tag, verify (try-start). Stored energy (gravity, springs, capacitors, pressure) kills after the disconnect is opened.
- Confined space: permit space = permit, attendant, rescue plan (non-entry preferred). Atmospheric testing: O₂ 19.5–23.5%, flammables <10% LEL, toxics below PEL — in that order, calibrated instruments.
- Excavation: 5 ft triggers protection (sloping/benching/shoring); spoil ≥2 ft from the edge; a competent person inspects daily. Cave-ins kill in minutes — the soil doesn't negotiate.
- Electrical (70E): arc-flash boundary, limited/restricted approach; de-energize unless infeasible. Shock and arc are different hazards with different boundaries.
Fire and emergency
- Extinguishers: A within 75 ft, B within 30–50 ft (by rating), K in kitchens, D where burning metal lives, C where energized equipment is. Match the class to the fuel, not the nearest cabinet.
- Egress: two ways out, travel distance by occupancy, exit signs and emergency lighting on backup power. Egress is the one life-safety system that must work with zero maintenance during the event.
- EAP: 1910.38 — alarm, evacuation, accounting, rescue/medical duties. Drills test the plan; the plan is not the drill.
Environmental
- RCRA generators: VSQG ≤100 kg/mo, SQG 100–1,000, LQG ≥1,000 (or >1 kg acute). Clocks: LQG 90 days, SQG 180. Crossing a threshold changes everything downstream.
- Mixture/derived-from: dilution never de-lists; residues inherit the listing.
- SPCC: 1,320 gal aggregate aboveground → plan required. Secondary containment sized for the largest tank plus precipitation.
- DOT placards: Table 1 any quantity; Table 2 at 1,001 lb. The 9 classes in order: explosives, gases, flammable liquids, flammable solids, oxidizers, toxics, radioactive, corrosives, miscellaneous.
- EPCRA: Tier II March 1, TRI Form R July 1. RQs: ammonia 100, chlorine 10, sulfuric acid 1,000, PCBs 1 lb — memorize the common ones.
Management systems
- PDCA: policy → planning → implementation → checking → review. The audit finding is almost always in "checking" (monitoring, investigation, corrective action) — programs fail at follow-through, not at policy-writing.
- Leading vs. lagging: TRIR is lagging; near-miss reporting rate, training completion, audit-closure time, and leadership visibility are leading. Manage the leading, report the lagging.
- Root cause: 5 whys (or fishbone, or TapRooT) — the cause is a system condition, not a person's mistake, until proven otherwise. "Retrain the employee" as the sole corrective action is the mark of a failed investigation.
- ALARP: reduce risk until further reduction is grossly disproportionate — the framework for every "how safe is safe enough" decision.
Human factors
- Just culture: errors are learning, violations are choices, recklessness is culpable — respond differently to each. Blame the system first.
- Fatigue: 12-h shifts, nights, overtime stacking — roster design is a safety control. The incident rate climbs in the last hours of long shifts.
- Risk perception: workers normalize deviance (the bypassed guard, the skipped step) — audits must look for what's actually done, not what's written.
Niche credentials worth knowing
- OHST (Occupational Hygiene and Safety Technologist) — the CCHEST technician tier below the professional credentials.
- CHST (Construction Health and Safety Technician) — BCSP's construction technician credential.
- ASP (Associate Safety Professional) — BCSP's associate tier on the CSP path.
- GSP (Graduate Safety Practitioner) — for ABET/QAP safety-program graduates; the direct CSP qualifier.
- STS (Safety Trained Supervisor) — BCSP's frontline-supervisor credential.
- EurOSHM — the European occupational safety and health manager framework; the EU-side counterpart.
Cross-discipline sanity checks
- Engineering: the hierarchy of controls is an engineering design principle — involve safety at the design stage (prevention through design), not after the guard is missing.
- Legal: General Duty Clause 5(a)(1) covers recognized hazards without a specific standard — "no standard for it" is not a defense.
- Environmental: safety incidents become environmental incidents (spills, releases) — the contingency plan covers both.
- Operations: production pressure is the latent condition behind most "worker error" — fix the incentive, not just the behavior.
Original ETS reference writing, verified against public sources on 2026-09-30. Thin sourcing is flagged inline. Not legal advice — confirm current editions with the issuing body.