Industrial Safety and Hazard Management

FE Exam Weight: Safety, Health, and Environment contributes 6–9 questions (~7% of the 110-question FE Other Disciplines exam). Expect definition recall (PEL vs. TLV, hierarchy of controls), a TWA or LEL calculation, and high-level environmental-regulation identification. Key tables live in the searchable NCEES FE Reference Handbook.

Industrial Hygiene

Industrial hygiene is the science of anticipating, recognizing, evaluating, and controlling workplace conditions that may cause illness or injury. Hazards group into five categories:

Hierarchy of Controls

Controls are ranked most to least effective; the exam routinely tests this order:

1. Elimination — remove the hazard entirely (most effective)
2. Substitution — replace with a less hazardous material/process
3. Engineering controls — isolate workers (ventilation, guarding, enclosure)
4. Administrative controls — change work practices (training, rotation, scheduling)
5. PPE — respirators, gloves, goggles (last resort)

Exam key: PPE is the LAST line of defense, not the first; engineering controls outrank administrative controls because they don't depend on worker behavior.

Exposure Limits and Toxicology

Time-weighted average: TWA = Σ(Cᵢ·tᵢ) ÷ 8 hours.

Worked example: 50 ppm for 3 h, 80 ppm for 2 h, 20 ppm for 3 h → TWA = (50·3 + 80·2 + 20·3)/8 = (150+160+60)/8 = 46.25 ppm — compare against the PEL/TLV.

Toxicology studies how dose affects harm. The dose–response curve plots effect versus dose; the LD50 (lethal dose for 50% of a test population) and LC50 (lethal airborne concentration) quantify acute toxicity — a lower LD50 means more toxic. Routes of entry are inhalation, absorption, ingestion, and injection. Effects may be acute (immediate) or chronic (long-term, e.g., silicosis, carcinogenesis).

Hazard Communication (GHS)

OSHA's Hazard Communication Standard adopts the Globally Harmonized System (GHS). Every hazardous chemical needs a standardized 16-section Safety Data Sheet (SDS) (formerly MSDS) and a label with a signal word ("Danger" or "Warning"), hazard statements, and pictograms (flame, skull-and-crossbones, health hazard, corrosion, etc.). Workers must be trained on these.

Noise, Atmosphere, and Flammability

Noise: OSHA requires a hearing conservation program at 85 dBA (8-hour TWA) and sets a 90 dBA PEL. Because decibels are logarithmic, a 3-dB rise roughly doubles sound energy and halves the allowable exposure time.

Atmosphere: a normal/safe atmosphere is 19.5–23.5% oxygen (< 19.5% deficient; > 23.5% enriched/fire risk; ambient ≈ 20.9%).

Flammability: a vapor ignites only between its LEL (Lower Explosive Limit) and UEL (Upper Explosive Limit); below LEL is too lean, above UEL too rich.

Confined Space, Electrical, and Fire Safety

A confined space is large enough to enter, has limited entry/exit, and is not designed for continuous occupancy. Permit-required entry demands: atmospheric testing first, mechanical ventilation, an outside attendant, communication, a rescue plan, an entry permit, and lockout/tagout (LOTO) of all energy sources.

Electrical: 50–600 V causes most electrocutions; LOTO de-energizes and locks equipment before maintenance, and arc-flash PPE is required at higher energy. Fire needs the fire-tetrahedron — fuel, oxygen, heat, chain reaction — and is fought by removing one; extinguisher classes are A (ordinary), B (flammable liquids), C (electrical), D (metals), and K (kitchen).

Risk and Environmental Regulation

Risk = probability × consequence (severity); controls aim to reduce one or both, and residual risk is documented. At a high level the FE expects awareness of major U.S. environmental statutes:

Personal protective equipment maps to the hazard: hard hats (head), safety glasses/goggles (eyes), earplugs/muffs (> 85 dBA), respirators (airborne), chemical gloves (hands), steel-toe boots (feet), and fall harnesses above ~6 ft.

Radiation safety distinguishes ionizing radiation (alpha, beta, gamma, X-ray, neutron — capable of breaking chemical bonds and damaging DNA) from non-ionizing radiation (UV, microwave, RF). Protection follows the ALARA principle (As Low As Reasonably Achievable) using the three classic controls: time (minimize exposure duration), distance (intensity falls with the inverse square of distance), and shielding (lead or concrete for gamma, plastic for beta). Dose is measured in rem or sievert.

These same time–distance–shielding ideas, plus the hierarchy of controls, tie the whole safety section together: identify the hazard, evaluate the exposure quantitatively, then control it at the highest feasible level.