CIH cheat sheet

8-hour TWA = Σ(Ci × Ti) ÷ 8, where Ci is concentration in each interval and Ti is its duration in hours; compare the result to the applicable OEL.

ppm to mg/m³: mg/m³ = ppm × molecular weight ÷ 24.45 (molar volume at 25 °C, 1 atm); use 24.05 at 20 °C.

Chronic dose by inhalation: Dose = (C × IR × ET × EF × ED) ÷ (BW × AT), where IR = inhalation rate, ET = exposure time, EF/ED = frequency and duration, BW = body weight, AT = averaging time.

Similar Exposure Groups (SEGs) group workers whose tasks, materials, and controls are alike; sampling within a SEG supports a decision about the whole group.

OSHA PELs are enforceable legal limits; ACGIH TLVs are health-based guidelines; NIOSH RELs are recommended limits; IDLH values apply to escape and respirator selection, not routine exposure limits.

Personal breathing-zone samples are the default for compliance; area samples are useful for engineering evaluation but do not represent individual exposure.

Wipe sampling expresses removable surface contamination as mass per area (e.g., µg/100 cm²) and cannot be compared directly with airborne OELs.

Exposure judgment combines monitoring data, modeling, and professional judgment; document assumptions, sample representativeness, and the confidence level of the decision.

Ceiling limits apply to any instantaneous or short-term peak and must never be exceeded; short-term exposure limits (STELs) are typically 15-minute averages.

Hierarchy of effectiveness: elimination > substitution > engineering controls > administrative controls > PPE; controls higher in the hierarchy protect more people with less reliance on behavior.

Local exhaust capture velocity: roughly 50–100 fpm at the source for low-toxicity contaminants and 100–200 fpm for more toxic agents; required velocity rises steeply with hood distance.

Dilution ventilation mass balance: Q = G ÷ (C − Ca), where Q = airflow, G = contaminant generation rate, C = target concentration, Ca = background concentration.

Hood airflow for a plain opening: Q = V(10X² + A), where V = capture velocity, X = distance from hood face, A = hood face area.

Maximum use concentration: MUC = APF × OEL; representative APFs are 10 for a half-mask air-purifying respirator, 50 for full-facepiece air-purifying, and 10,000 for pressure-demand SCBA.

Hearing protector derating per OSHA: attenuation = (NRR − 7) × 0.5; NIOSH applies a 25% derating instead of 50%.

Air-purifying cartridge change schedules must be based on challenge concentration, cartridge capacity, breathing rate, temperature, and humidity - not on odor detection.

Administrative controls (rotation, reduced task duration) reduce individual dose only if the exposed person's time near the source actually decreases.

Four-step risk assessment framework: hazard identification, dose-response assessment, exposure assessment, and risk characterization.

Noncancer screening: Hazard Quotient = exposure ÷ RfD; a Hazard Index sums HQs for chemicals affecting the same target organ; HI ≤ 1 is generally considered acceptable.

Cancer risk = chronic daily intake × cancer slope factor; a risk in the 1×10⁻⁶ to 1×10⁻⁴ range is commonly used as a decision band.

RfD is derived by dividing a NOAEL or LOAEL by uncertainty factors, typically 10× for animal-to-human extrapolation and 10× for human variability.

The cancer slope factor is an upper-bound estimate of risk per unit dose, derived from the low-dose slope of the dose-response curve.

Mode of action determines whether low-dose extrapolation should be linear (default for carcinogens without a threshold) or nonlinear/threshold-based.

Biological Exposure Indices (BEIs) are reference values for measured biological parameters (urine, blood, exhaled air) that correspond to inhalation exposure at the TLV.

Risk characterization states the estimated risk, the key assumptions, the populations evaluated, and the sources of uncertainty.

Air dispersion models such as AERMOD and ISC predict downwind concentrations from emission rate, stack parameters, meteorology, and terrain using Gaussian plume assumptions.

Community exposure routes include inhalation, soil and dust ingestion, drinking water, and consumption of homegrown produce; aggregate risk sums across all pathways and media.

Children receive higher dose per unit body weight and have hand-to-mouth behavior; early-life susceptibility requires age-specific intake factors.

Acute guidance values for community emergencies: AEGL-1/2/3 and ERPG-1/2/3 describe escalating severity at defined exposure durations.

Fenceline and ambient monitoring are compared against National Ambient Air Quality Standards or site-specific risk-based screening levels.

Environmental justice principles require evaluating whether minority or low-income populations bear disproportionate environmental burden.

Odor thresholds are often far below health-based limits; odor complaints are managed through nuisance provisions rather than toxicity criteria.

Risk-based screening levels (RBSLs) for soil, groundwater, and air are back-calculated from a target risk level and site-specific exposure assumptions.

The Plan-Do-Check-Act cycle underpins ISO 45001 and ISO 14001 management systems and drives continual improvement of EHS performance.

Leading indicators (training completed, inspections performed, corrective actions closed) predict future performance; lagging indicators (injury rates, incidents) measure past outcomes.

Risk communication must account for outrage factors - dread, involuntary exposure, unfamiliarity, and inequity - which amplify perceived risk beyond the technical estimate.

Management of change is a formal review that identifies and controls hazards introduced by changes in process, equipment, materials, or staffing before implementation.

Program justification uses the business case: direct costs (workers' compensation, fines), indirect costs (productivity, turnover, reputation), balanced against control costs.

Resource allocation should follow a documented risk-ranking method so that limited budget goes to the highest residual risks first.

Span of control in managed teams and incident organizations is typically 3 to 7 direct reports for effective supervision.

Documented decisions and their rationale support defensibility, continuity when staff change, and organizational learning.

HAZWOPER (29 CFR 1910.120) training: 40 hours for general site workers, 24 hours for occasional site visitors under supervision, and 8-hour annual refreshers for both.

Level A = fully encapsulating chemical-protective suit with SCBA; Level B = chemical-resistant clothing with SCBA; Level C = chemical-resistant clothing with air-purifying respirator; Level D = work clothing only.

Emergency response is organized under the Incident Command System with unified command, defined roles (incident commander, safety officer, operations, planning, logistics, finance), and a span of control of 3–7.

Exposure guidance tiers: AEGL-1/ERPG-1 = mild transient effects; AEGL-2/ERPG-2 = irreversible or serious effects; AEGL-3/ERPG-3 = life-threatening effects.

Site control uses three zones - exclusion (hot), contamination reduction (warm), and support (cold) - with decontamination at the boundary between hot and warm.

An emergency action plan must specify escape routes, alarm systems, headcount procedures, rescue duties, and shutdown responsibilities.

Shelter-in-place is preferred over evacuation when outdoor concentrations are higher than indoor levels or when evacuation would move people through the release.

Medical surveillance and post-exposure evaluation are required after significant exposures and for members of hazardous waste response teams.

The ABIH Code of Ethics requires holding paramount the health and safety of workers and the public, above employer, client, or personal interest.

Conflicts of interest - financial, personal, or organizational - must be disclosed before accepting an assignment or rendering an opinion.

Personal medical and exposure records are confidential; disclosure is limited to what is legally required or authorized by the individual.

Practitioners must work only within their education, training, and experience, and must refer out matters outside their competence.

Data, credentials, and conclusions must never be misrepresented; contrary findings and uncertainty must be reported honestly.

Suspected violations of the code are reported to the certifying board, which applies a defined disciplinary process.

Whistleblower protections cover employees who report illegal or unsafe conditions to regulators after internal channels fail.

Gifts, fees, or hospitality that could reasonably influence professional judgment should not be accepted.