Glossary

Sound pressure level in decibels weighted to approximate the frequency sensitivity of the human ear. The standard unit for occupational noise exposure assessment. dBA attenuates low- and high-frequency sounds relative to the mid-range.

A1 — Confirmed Human Carcinogen, on the weight of evidence from epidemiologic studies. A2 — Suspected Human Carcinogen: human data adequate but conflicting or insufficient, or carcinogenic in animals by a route or mechanism relevant to workers. A3 — Confirmed Animal Carcinogen with Unknown Relevance to Humans: carcinogenic in animals at high dose by a route that may not be relevant, with no confirmed human risk. A4 — Not Classifiable: concern exists but there is not enough data to assess. A5 — Not Suspected as a Human Carcinogen, on the basis of adequate negative epidemiology. The absence of a category does NOT mean the substance is safe — ACGIH assigns no designation where no carcinogenicity data exist at all, so a blank means untested and A5 means tested and cleared. For A1, A2 and A3, Appendix A requires exposure by all routes to be controlled to levels as low as possible below the TLV; for an A1 carcinogen with no TLV, exposure should be eliminated to the fullest extent possible.

The radioactivity per unit mass or volume of a material. Expressed as Bq/g or Bq/kg for solids; Bq/L or Bq/m³ for liquids; Bq/m³ for gases and air. The primary metric for NORM screening and clearance decisions.

ACGIH Appendix E: where two or more substances act on the same target organ or system, their combined effect governs. If Σ(Cᵢ/Tᵢ) exceeds unity the limit for the mixture is exceeded. Limit types should be consistent — TWA with TWA, STEL with STEL — and where a substance with a STEL is mixed with one having only a TLV-TWA, the latter may enter the short-term sum at five times its TWA. The formula does not apply to consecutive exposures of ceiling limits.

The number of times the total air volume of a space is replaced per hour by ventilation. Used to quantify dilution ventilation effectiveness. Required ACH for gas/vapour dilution depends on release rate, LEL, and mixing quality.

Australian Radiation Protection and Nuclear Safety Agency — the national body responsible for radiation protection standards, regulation, and guidance in Australia. Sets clearance levels and occupational dose limits for Australian workplaces.

A radiation protection principle requiring that exposures be minimised as far below regulatory limits as is reasonably achievable, considering economic and social factors. Applied in all radiation work.

A risk management principle requiring that risk be reduced until the cost and effort of further reduction would be grossly disproportionate to the benefit gained. Central to UK and Australian safety law.

A thermophilic mould (optimal growth 37–50°C) that can cause invasive aspergillosis in immunocompromised individuals and hypersensitivity pneumonitis in healthy workers. The primary fungal target in composting, waste handling, and mould remediation.

The level of respiratory protection that a correctly selected, fitted, and used respirator is expected to provide in the workplace. Used to determine whether a respirator is adequate for a given exposure concentration.

A NIOSH equation multiplier for the angle (A°) of asymmetric body rotation during the lift. AM = 1 − 0.0032A. Zero at A = 135°. Penalises lifts that require significant torso rotation away from the mid-sagittal plane.

Atmosphères Explosibles — the EU regulatory framework governing equipment and protective systems for use in potentially explosive atmospheres. Comprises Directive 2014/34/EU (equipment) and Directive 1999/92/EC (worker protection). Defines equipment zones (0/1/2 gas; 20/21/22 dust).

A polysaccharide cell wall component of fungi associated with inflammatory airway effects and sick building syndrome. No formal OEL exists in any jurisdiction; concentrations >200 ng/m³ have been associated with health effects in some studies.

The SI unit of radioactivity. 1 Bq = one nuclear disintegration per second. Replaces the older unit Curie (Ci); 1 Ci = 3.7 × 10¹⁰ Bq. Used to express both activity concentration (Bq/g, Bq/m³) and total activity (Bq).

A substitution method for non-detects (Ganser and Hewett, 2010) that replaces each non-detect with its LOD multiplied by a factor computed from the detected values and the share of non-detects, with separate factors for estimating the arithmetic and the geometric mean. It is far less biased than LOD/2 or LOD/√2. It is not maximum likelihood or regression on order statistics, which treat non-detects as censored. The Exposure Profiler does not implement it: its 0.65 × LOD option is a fixed fraction.

Airborne particles of biological origin capable of causing infection, allergy, or toxicity. Includes bacteria, fungi, viruses, endotoxins, glucans, pollen, and animal-derived proteins. Size ranges from <0.01 µm (viruses) to >100 µm (fungal spores).

A US CDC/NIH classification (BSL-1 to BSL-4) describing the containment precautions required to handle biological agents of varying hazard potential. Similar systems: WHO risk groups 1–4; EU containment levels 1–4.

A shift OEL adjustment model by Brief and Scala (1975) that applies two correction factors: one for increased daily exposure hours and one for reduced recovery time between shifts. Widely used and generally conservative.

Sound pressure level in decibels with a flatter frequency response than dBA. Used primarily for peak sound measurement (impulse/impact noise). Occupational peak limits (140 dBC) are compared against dBC readings.

A qualifier indicating that a substance is classified as a confirmed, probable, or possible human carcinogen. Often triggers additional controls, monitoring, and biological surveillance regardless of measured airborne concentration.

An airborne concentration that must not be exceeded at any point during the working day. Applied to substances with acute toxicity where even brief exceedances are hazardous.

Measurements reported only as "less than" a threshold value (e.g., < 0.05 mg/m³), because the true value is below the analytical detection or quantitation limit. Censored values carry information (an upper bound) but no specific value. Require special statistical methods for analysis.

A correction added to the measured WBGT to account for the reduced evaporative heat loss caused by certain protective clothing. For example: disposable coveralls add 0 °C; impermeable suits add 10–12 °C.

A unit of measurement for viable bacteria or fungi in air or surface samples. One CFU represents a single colony grown on culture media from one viable propagule (cell, spore, or aggregate). Measured as CFU/m³ for air samples.

The standard uncertainty of a derived quantity, combining individual standard uncertainties using the law of propagation of uncertainty. For independent, uncorrelated sources: uc = √(Σuᵢ²). Accounts for all significant uncertainty contributors.

A portable instrument for measuring flammable gas concentrations in air, typically expressed as % LEL. Required for atmospheric monitoring before and during confined space entry. Must be calibrated to the specific gas being monitored.

An extension of the NIOSH equation for jobs involving multiple distinct lifting tasks. Tasks are ranked by LI (highest first) and combined using a cumulative frequency summation method. Always ≥ the highest individual LI.

An enclosed or partially enclosed space not designed for continuous human occupancy that may present atmospheric, engulfment, or other hazards. Requires risk assessment, atmospheric monitoring, a permit system, and rescue procedures before entry. Defined in OSHA 1910.146, AS 2865, and EN 365.

A qualitative risk management approach that assigns a chemical to one of four control approaches (CB1–CB4) from its hazard group, the quantity used and its dustiness or volatility. CB4 ("seek specialist advice") applies to every substance in hazard group E (carcinogens, mutagens and respiratory sensitisers) and to the highest hazard and quantity combinations. Standardised by ILO and UK HSE COSHH Essentials.

A NIOSH equation multiplier for the quality of the hand–load interface. Good coupling (CM = 1.00): optimal handles or hand-holds; Fair (CM = 0.95): acceptable grip with some compromise; Poor (CM = 0.90): fingers flexed 90°, no handles.

The multiplier applied to the combined standard uncertainty to define the expanded uncertainty. Common values: k = 1.645 (90% confidence, normal distribution); k = 1.96 (95%); k = 2 (≈95%); k = 3 (99.7%). Higher k → wider, more conservative uncertainty interval.

The permissible noise level for an 8-hour working day established by a given standard. NIOSH and ACGIH use 85 dBA; OSHA uses 90 dBA. The criterion level defines when 100% of the permissible dose is reached at 8 hours.

The 8-hour energy-equivalent frequency-weighted acceleration (m/s²) representing daily vibration dose. Calculated as the root-mean-square acceleration scaled to an 8-hour reference period. Compared against EAV and ELV.

A NIOSH equation multiplier for vertical travel distance (D) of the load from origin to destination. DM = 0.82 + 4.5/D (cm). Penalises large lifting ranges; optimal at D = 25 cm.

The calendar day on which a shift starts. Counting this way means a night shift crossing midnight is one duty day rather than two, which matters when testing the model Code of Practice guidance not to work more than five days in a row.

Electric and magnetic fields generated by electricity generation, transmission, and use, as well as wireless communication devices. Categorised by frequency: static (0 Hz), ELF (1–300 Hz), IF (300 Hz–100 kHz), RF/microwave (100 kHz–300 GHz).

A unit of energy equal to the kinetic energy gained by a single electron accelerating through a potential difference of one volt (1 eV ≈ 1.602 × 10⁻¹⁹ J). Used in PID technology to express both lamp energy (common values: 9.8, 10.6, and 11.7 eV) and compound ionisation energies (IE). A compound responds to a given lamp only if its IE is strictly less than the lamp energy.

A lipopolysaccharide (LPS) component of the outer membrane of Gram-negative bacteria. Released on bacterial death; causes inflammation, airway obstruction, and systemic effects (cotton dust disease, organic dust toxic syndrome). Measured in Endotoxin Units (EU) per m³.

The measurement unit for airborne endotoxin concentration. The ACGIH TLV-L (inhalable fraction) is 90 EU/m³. No formal OEL exists in most other jurisdictions. High exposures occur in agriculture, sewage treatment, and food processing.

The constant sound level that would deliver the same total acoustic energy as the actual varying noise over the same time period. Calculated using the logarithmic energy-average of measured levels. The foundation of all noise dose calculations.

European Directive establishing minimum health and safety requirements for workers exposed to physical agents (vibration). Sets EAV and ELV for hand-arm and whole-body vibration; implemented in national legislation across EU member states.

The estimated proportion of daily exposures expected to exceed the OEL. Used as the primary risk metric in the AIHA strategy. Risk categories: < 1% exceedance = acceptable; 1–5% = uncertain; > 5% = unacceptable. Calculated from the lognormal distribution parameters.

The increase in sound level (in dB) that halves the allowable exposure time. NIOSH and ACGIH use a 3 dB exchange rate (equal-energy principle); OSHA uses 5 dB. The 3 dB rate is scientifically preferred.

The ACGIH rule that applies where a TLV-TWA has no accompanying STEL: excursions may exceed three times the TLV-TWA for no more than 15 minutes at a time, on no more than four occasions spaced an hour apart in a workday, and under no circumstances exceed five times it, provided the TLV-TWA itself is not exceeded. It is a default in the absence of a published short-term limit, not a cap on what a regulator may publish, so a STEL set above three or five times its own TWA breaches nothing. Comparing a published STEL against its own TWA also says nothing about how permissive that limit is in absolute terms: a jurisdiction with a very low 8-hour limit can show a large multiple while still publishing the lowest short-term value of any jurisdiction.

The combined standard uncertainty multiplied by a coverage factor k. U = k × uc. Represents an interval within which the true value is expected to lie with a defined probability. For k = 2 (approximately 95% confidence): U = 2uc.

Under the EU Physical Agents Directive: the vibration or noise level at which employers must act — implementing a programme of controls, health surveillance, and worker information. HAV EAV: A(8) = 2.5 m/s²; WBV EAV: A(8) = 0.5 m/s².

Under the EU Physical Agents Directive: the maximum daily vibration or noise exposure a worker may receive. Exceeding the ELV requires immediate intervention. HAV ELV: A(8) = 5.0 m/s²; WBV ELV: A(8) = 1.15 m/s².

The EMF frequency range from 1 Hz to 300 Hz; includes the power frequency (50 Hz in Europe/Australia, 60 Hz in North America). The principal ELF exposure source for most workers is power lines, switchgear, and transformers.

Mental or physical exhaustion that reduces the ability to perform work safely and effectively. The model Code of Practice: Managing the risk of fatigue at work (Safe Work Australia) treats it as a hazard to be managed through work design — hours, shift timing, breaks and workload — rather than through the worker's own effort to stay alert. It is not the same as ordinary tiredness: the concern is the measurable loss of performance, judgement and reaction time.

A record of the fatigue-related hazards present in the work itself — hours, workload, task demand, environment, individual and organisational factors — with the controls applied to each. It is the qualitative half of a fatigue assessment; a roster analysis is the quantitative half, and neither substitutes for the other.

A unit of airborne fibre concentration used for asbestos and man-made fibres. Counted using phase contrast microscopy (PCM) per NIOSH 7400. The OSHA asbestos PEL is 0.1 f/cc (8-hour TWA).

The concentration range between the LEL and UEL within which a gas–air mixture can ignite and sustain combustion. Also called the explosive range. The wider the range, the more dangerous the substance. Hydrogen (4–75%) has a very wide flammable range.

The minimum temperature at which a liquid produces sufficient vapour to form an ignitable mixture near the surface when exposed to an ignition source. A key parameter in flammability hazard classification. Not the same as the auto-ignition temperature.

A shift pattern that moves later through the day as it progresses — day to evening to night. The model Code of Practice recommends forward rotation when transitioning between shifts, because the body clock adjusts more readily to a delayed sleep period than to an advanced one. A backward rotation moves the other way and is the pattern to avoid.

A NIOSH equation multiplier for lifting frequency (lifts/min) and shift duration. Values derived from NIOSH Table 5; accounts for both metabolic and musculoskeletal fatigue effects of repetitive lifting.

The root-mean-square acceleration measured at the hand-tool interface for HAV assessment, weighted by the frequency response of the Wh filter (ISO 5349). Measured in m/s².

A calendar day with no worked minutes at all. A night shift that crosses midnight therefore consumes part of the following day and that day is not a full day off. The model Code of Practice asks for at least one per week; a roster is tested over every rolling window of seven consecutive days, not over the calendar week.

The central tendency measure for lognormally distributed data (the standard model for occupational exposure measurements). Calculated as the antilog of the arithmetic mean of log-transformed values: GM = exp(mean of ln(xᵢ)). More representative than the arithmetic mean for skewed data.

The measure of spread for lognormally distributed data. Calculated as exp(standard deviation of ln(xᵢ)). A GSD of 1.0 indicates no variability; typical occupational exposure data shows GSD of 2–4. GSD > 3 indicates high variability.

Temperature measured by a thermometer positioned at the centre of a 150 mm matte black copper sphere. Reflects radiant heat load (sun, hot surfaces, furnaces) in addition to air temperature.

The international standard (JCGM 100:2008, ISO/IEC Guide 98-3) defining how to evaluate and express measurement uncertainty. The GUM establishes the framework for Type A and Type B uncertainty evaluation and the law of propagation of uncertainty.

Mechanical vibration transmitted to the hand and arm through vibrating tools (grinders, drills, chainsaws, etc.). Prolonged exposure causes Hand-Arm Vibration Syndrome (HAVS), including vibration white finger (VWF) and peripheral neuropathy. Assessed per ISO 5349.

A structured programme required when workers are exposed at or above the action level. Includes: noise monitoring, audiometric testing (baseline and annual), hearing protector provision, training, and recordkeeping.

The physiological adaptation to heat stress that occurs over 1–2 weeks of graded heat exposure — including increased plasma volume, earlier onset of sweating, and lower core temperature response. Significantly increases heat tolerance and reduces risk.

An apparent temperature combining air temperature and relative humidity to estimate how hot it feels to the body. Used when WBGT measurement equipment is unavailable. NIOSH and OSHA publish action thresholds in both WBGT and Heat Index.

A framework for selecting control measures in order of effectiveness: (1) Elimination, (2) Substitution, (3) Engineering controls, (4) Administrative controls, (5) Personal protective equipment. Higher-level controls are always preferred.

A NIOSH equation multiplier penalising horizontal distance (H) between the midpoint of the ankles and the hands at lift origin. HM = 25/H (cm). Optimal at H = 25 cm; zero at H ≥ 63 cm (outside recommended reach zone).

Activity concentration or total activity below which NORM-containing material may be released from regulatory control without further radiological consideration. Defined in IAEA Safety Standards (RS-G-1.7); varies by radionuclide and exposure pathway.

International Commission on Non-Ionizing Radiation Protection — an independent scientific body publishing evidence-based exposure guidelines for non-ionising radiation (static fields, ELF, IF, RF/microwave, UV, visible, IR, laser). The low action levels of EU Directive 2013/35/EU from 1 Hz to 10 MHz equal the ICNIRP 2010 occupational reference levels.

International Electrotechnical Commission System for Certification to Standards Relating to Equipment for Use in Explosive Atmospheres. An internationally recognised certification scheme equivalent to ATEX; accepted in Australia, Asia, and many other non-EU jurisdictions.

The maximum airborne concentration from which an unprotected worker could escape within 30 minutes without experiencing impairing symptoms or irreversible health effects. Set by NIOSH; used to define minimum respirator requirements.

The science and practice of anticipating, recognising, evaluating, and controlling workplace environmental stressors (chemical, physical, biological, ergonomic) that may cause injury, illness, or discomfort to workers.

The EMF frequency range from 300 Hz to 100 kHz. Sources include induction heating, anti-theft systems, wireless charging pads, and some medical devices. Covered by ICNIRP 2010 guidelines and EU Directive 2013/35/EU.

The minimum energy required to remove an electron from a gas-phase molecule, expressed in electron volts (eV). A PID lamp cannot ionise compounds whose IE is equal to or greater than the lamp energy, resulting in No Response (NR). Compounds with IE below the lamp energy will respond, with sensitivity broadly increasing as the margin between lamp energy and IE widens.

The radiant power incident per unit area of surface; expressed in W/m². The primary measurement quantity for UV, visible, and infrared optical radiation assessment. Used to calculate dose (radiant exposure) when multiplied by duration.

International standard for the measurement and evaluation of human exposure to whole-body vibration and repeated mechanical shock. Part 1 (1997) is the primary standard for occupational WBV assessment.

International standard for the measurement and evaluation of human exposure to hand-transmitted vibration. Part 1 covers general requirements; Part 2 covers practical guidance for measurement at the workplace.

A colourless flammable gas (2-methylpropene, CAS 115-11-7) used as the universal calibration reference for PIDs. All major manufacturers define isobutylene's correction factor as 1.00 at all lamp energies. CF values for all other compounds are expressed relative to the isobutylene response.

A Gram-negative bacterium that causes Legionnaires' disease (severe pneumonia with ~10% case fatality rate) and Pontiac fever when inhaled as fine aerosol droplets from contaminated water. Proliferates at 25–45°C in biofilm-containing water systems.

The ratio of the actual load lifted to the RWL. LI < 1: low risk; LI 1–3: moderate risk, engineering review warranted; LI ≥ 3: high risk, immediate intervention recommended.

The lowest concentration at which the analytical method can reliably distinguish the analyte signal from background noise with a stated confidence (typically 99%). Concentrations below the LOD are reported as non-detects (< LOD) — i.e., censored data.

The lowest concentration at which the analyte can be measured with acceptable precision and accuracy. Typically 3–10× the LOD. Concentrations between the LOD and LOQ may be reported with a precision caveat. Generally preferred as the reporting threshold in exposure data.

The maximum recommended load under ideal conditions in the NIOSH lifting equation. LC = 23 kg (51 lb). All other multipliers (HM, VM, DM, AM, FM, CM) reduce this value based on task conditions.

A simple substitution method for non-detect values: replace < LOD with LOD ÷ √2 ≈ 0.707 × LOD. Recommended by several industrial hygiene guidance documents for censoring < 50%. Produces less bias than LOD/2 when the true value is uniformly distributed between 0 and LOD.

A simple substitution method replacing non-detect values with half the LOD. Easy to implement but tends to overestimate central tendency (upward bias) compared to LOD/√2 or maximum likelihood estimation methods. Use with caution when > 30–50% of values are non-detects.

A probability distribution where the natural logarithm of the variable is normally distributed. The standard model for occupational airborne exposure data. A dataset is lognormal if values plotted on log-probability paper fall approximately on a straight line.

The window in the circadian cycle where alertness is lowest and the risk from an individual mistake is highest, named in the model Code of Practice as roughly 02:00-06:00. The code advises avoiding tasks with a high consequence of error, such as driving, during this period.

The minimum concentration of a flammable gas or vapour in air below which the mixture is too lean to ignite and sustain combustion. Expressed as % v/v or ppm. Below the LEL, there is insufficient fuel for ignition.

A unit of metabolic rate relative to resting; 1 MET ≈ 58 W/m² (1 kcal/kg/hr). Sedentary work ≈ 1–1.5 MET; moderate physical work ≈ 3–5 MET; heavy work ≈ 6–8 MET.

The rate of energy production by the body during work; determines the internal heat load that must be dissipated. Expressed in watts (W) or W/m² body surface area. Ranges from ~80 W (resting) to >600 W (very heavy manual work).

A mass concentration unit expressing milligrams of airborne substance per cubic metre of air. Used for particles (dusts, fibres), aerosols, and low-volatility substances, as well as some gases and vapours alongside ppm.

Temperature measured by a thermometer with a wetted wick exposed to natural (unforced) airflow. Reflects evaporative cooling capacity — a key determinant of the body's ability to lose heat through sweating.

Materials containing naturally occurring radionuclides (uranium, thorium, radium, radon, and their decay products) at concentrations that may require regulatory oversight due to elevated occupational or public exposure.

A shift worked through the biological night. The model Code of Practice does not define one, so an assessment has to state its own rule: the Exactus tool counts a shift as a night shift when it overlaps 00:00-05:00 by at least one hour, and treats a run of them as broken by any gap of 24 hours or more. The code advises against rostering more than three successive night shifts.

A biomechanical and epidemiological model for evaluating two-handed, sagittal-plane manual lifting tasks. Published by NIOSH (Waters et al., 1994). Produces a Recommended Weight Limit (RWL) and Lifting Index (LI). The CLI extension handles multi-task jobs.

A designation in a PID correction factor table indicating that a compound's ionisation energy (IE) meets or exceeds the lamp energy, preventing ionisation and producing no usable signal. A compound that shows NR on a 10.6 eV lamp may respond on an 11.7 eV lamp if its IE falls between the two values. Do not infer a zero concentration from an NR result — use a higher-energy lamp or an alternative detection method.

The fraction of the permissible daily noise exposure consumed, expressed as a percentage. A dose of 100% means the full permissible exposure has been reached. Dose can exceed 100%, indicating an exposure beyond the regulatory limit.

A US EPA measure of hearing protector attenuation under ideal laboratory conditions. Because real-world attenuation is lower, NIOSH recommends derated values: NRR×50% (earmuffs), NRR×30% (formable earplugs), NRR×70% (all earplugs used as labelled).

A finding status meaning the roster does not carry the information a control needs, so no verdict is given. Notice of a shift is the common case: where notice has not been recorded, the shift is reported as not assessable rather than as meeting the control. A gap in the input is not evidence of compliance.

A regulatory or recommended airborne concentration of a substance to which workers may be exposed repeatedly without adverse health effects. Includes PELs (OSHA), RELs (NIOSH), TLVs (ACGIH), and WES (Australia).

An atmosphere with less than 19.5% oxygen by volume at sea level. Causes impaired judgment and coordination at 16–18%; unconsciousness at <10–12%; death within minutes at <6%. Can occur without warning in confined spaces due to displacement, consumption, or chemical reaction.

ACGIH Appendix B guidance of 3 mg/m³ respirable and 10 mg/m³ inhalable for particles that have no TLV of their own, are insoluble or poorly soluble, and have low toxicity. It is explicitly a GUIDELINE and not a TLV, because the evidence does not meet the standard ACGIH requires to set one. ACGIH records that this entry and its predecessors have been misused by applying them to any unlisted particle rather than only to particles meeting all three conditions. Also called PNOR (particulates not otherwise regulated) and PNOC (not otherwise classified).

A dimensionless concentration unit expressing parts of substance per million parts of air by volume (ppmv) at a given temperature and pressure. Commonly used for gases and vapours. Convert to mg/m³ using: mg/m³ = ppm × MW / 24.45 (at 25°C, 1 atm).

Legally enforceable occupational exposure limits set by OSHA for US workplaces. PELs are based on 1968 ACGIH TLVs and are widely considered outdated; NIOSH RELs and ACGIH TLVs are generally more health-protective.

Equipment worn by a worker to minimise exposure to occupational hazards. Examples include respirators, hearing protectors, safety glasses, gloves, and high-visibility clothing. The last resort in the hierarchy of controls.

A shift adjustment approach using the biological half-life (t½) of a substance to estimate tissue accumulation at steady state for non-standard schedules. No adjustment is applied if t½ < 4 hours or t½ > 400 hours (insufficient accumulation).

A direct-reading instrument that measures airborne volatile organic compound (VOC) concentrations by ionising gas molecules with a UV lamp and detecting the resulting ion current. PIDs are fast, sensitive to sub-ppm levels, and widely used for screening surveys, leak detection, and short-term exposure assessments. They require a compound-specific correction factor (CF) because the instrument is calibrated to isobutylene, not the target compound.

A compound-specific multiplier applied to a raw PID reading to give the true concentration of the target compound: true concentration = PID reading × CF. CF values are determined empirically by each manufacturer using their specific instrument and lamp; they are not interchangeable between instruments or lamp energies. CF = 1.00 is assigned to isobutylene, the universal PID calibration gas. Some manufacturers label the same quantity as a Response Factor (RF) — this is a naming convention difference, not a methodological one, and is distinct from the shift-adjustment Reduction Factor (RF) used in OEL adjustment.

The radiant power per unit area, expressed in W/m². The primary ICNIRP reference level for RF and microwave fields above 10 MHz. The ICNIRP occupational reference level for 0.1–10 GHz is 50 W/m²; for the general public it is 10 W/m².

The time required to reduce a gas concentration from an initial level to a target safe level (typically 10% LEL) by mechanical ventilation. Calculated from volume, ventilation flow rate, and the log ratio of initial to target concentration.

The total radiant energy per unit area delivered over an exposure duration; H = E × t. Expressed in J/m². Compared against ACGIH TLV-L limits for UV and other optical radiation bands.

A naturally occurring radioactive noble gas produced by the decay of radium-226 in the uranium-238 decay series. The single largest natural source of ionising radiation dose to the public. Measured as Bq/m³ in air; IAEA reference level: 300 Bq/m³.

ACGIH Appendix H method for deriving a single exposure limit for a refined hydrocarbon solvent, whose hundreds of components mostly have no TLV. The liquid mass is grouped into hydrocarbon classes, each with a group guidance value, and combined as 1/GGV_mixture = Σ(Fₙ/GGVₙ). It applies only to saturated aliphatics and aromatics as vapours, over a boiling range under 45 °C. Benzene is excluded and must be monitored separately. Components with critical effects beyond the mixture basis — n-hexane, toluene, naphthalene, methylnaphthalene, indene — must be identified and monitored individually.

Non-regulatory occupational exposure guidelines issued by NIOSH based on current health evidence. RELs are often more stringent than OSHA PELs and are considered best-practice targets.

The maximum load (kg) that a healthy worker can lift under the specified task conditions for up to 8 hours without substantially increasing the risk of low-back musculoskeletal disorder. RWL = LC × HM × VM × DM × AM × FM × CM.

The multiplier applied to the standard OEL when adjusting for extended work shifts. RF values < 1 represent tightened limits for longer shifts. The adjusted OEL = standard OEL × RF.

ICNIRP's operational quantity for EMF — a measurable field strength (E-field in V/m; H-field in A/m; B-field in T; power density in W/m²) that, if not exceeded under worst-case assumptions, ensures the basic restriction (specific absorption rate) is not exceeded.

A subset of PPE specifically designed to protect the wearer's respiratory system from airborne contaminants including gases, vapours, dusts, and biological agents. Selection is based on contaminant type, concentration, and oxygen level.

The highest total of worked hours in any 168-hour window of a roster, rather than in a fixed Monday-to-Sunday week. The model Code of Practice reports beyond 39 hours per week over a prolonged period as leading to a decline in mental and physical health, and 55 or more hours as a serious health hazard. Both are stated as health findings rather than as roster control measures.

Modification of the 8-hour OEL to account for extended or non-standard work shifts. Methods include Brief & Scala (pharmacokinetic), OSHA category model, Quebec/IRSST, and Pharmacokinetic (half-life based). Always produces a lower adjusted OEL for shifts >8 hours.

The maximum concentration to which workers can be exposed for 15 minutes up to four times per day, with at least 60-minute intervals between exposures. Protects against acute effects from brief high-concentration exposures.

A group of workers with sufficiently similar tasks, locations, and exposures that any worker in the group could represent any other for monitoring purposes. Used to prioritise and design industrial hygiene sampling strategies.

A European measure of hearing protector attenuation calculated per ISO 4869-2. The protected level is approximated as L_Ceq − SNR. The EU Directive on PPE (89/686/EEC) requires SNR labelling on European hearing protectors.

A qualifier on an OEL indicating that the substance can be absorbed through intact skin in amounts that may contribute significantly to total body burden. Workers with skin notation substances require skin protection in addition to respiratory controls.

A period free of work long enough, and placed well enough in the night, for a normal sleep. The model Code of Practice asks for at least two consecutive nights of sleep opportunity between shift blocks but defines neither term, so an assessment has to state its own: the Exactus tool counts a 22:00-06:00 window entirely free of work as one night, and treats a gap of 24 hours or more as the boundary between blocks. Sleep OPPORTUNITY is not sleep obtained — a roster can only provide the window.

The rate at which energy from an electromagnetic field is absorbed by biological tissue, expressed in W/kg. The ICNIRP basic restriction for RF fields. Cannot be directly measured in workers; reference levels are set so that SAR limits are not exceeded under typical exposure conditions.

The uncertainty of a measurement result expressed as a standard deviation. Evaluated by Type A methods (statistical analysis of repeated measurements) or Type B methods (non-statistical: manufacturer specifications, calibration certificates, scientific judgement). Per GUM (JCGM 100:2008).

The exposure value below which 95% of all exposures in the population are expected to fall. The primary metric for characterising the upper tail of the exposure distribution and assessing compliance with OELs in the AIHA exposure assessment strategy.

NORM whose radioactivity has been concentrated or redistributed through industrial processing, making it a more significant radiation hazard than the original material. Common industries: oil and gas (scale), mining, fertiliser production, water treatment.

A valve blending hot and cold water to deliver a preset safe temperature at the point of use, reducing scalding risk (typically 38–42°C for most outlets). TMVs must be serviced regularly; if set too low or poorly maintained, they provide an ideal environment for Legionella growth.

Occupational exposure guidelines published annually by ACGIH. TLVs represent conditions under which nearly all workers may be repeatedly exposed without adverse health effects. Three types: TLV-TWA, TLV-STEL, and TLV-C (ceiling).

The average airborne concentration of a contaminant calculated over a defined reference period, typically 8 hours. The primary metric compared against OELs.

The maximum load a worker can sustain over a given work duration in a given thermal environment without exceeding physiological heat strain limits, per ISO 7933 / NIOSH. Accounts for WBGT, metabolic rate, and clothing.

The maximum concentration of a flammable gas or vapour above which the mixture is too rich to ignite in air (insufficient oxygen). Concentrations above the UEL may be extremely dangerous if diluted back into the flammable range.

Ultraviolet radiation is divided into UV-C (100–280 nm; germicidal, most biologically active), UV-B (280–315 nm; erythemal, solar), and UV-A (315–400 nm; photosensitising, blacklight). ACGIH TLV-L limits vary markedly by band.

The pressure exerted by a vapour in equilibrium with its liquid phase at a given temperature. High vapour pressure indicates high evaporation rate and greater inhalation exposure potential. Used to assess volatility hazard.

A safety factor in dilution ventilation design accounting for imperfect mixing of supply air with contaminant. Typical values: k = 3 (good mixing, supply near source); k = 5 (moderate mixing, typical indoor); k = 10 (poor mixing, general dilution only).

A NIOSH equation multiplier accounting for vertical hand height (V) at lift origin. VM = 1 − 0.003|V − 75|. Optimal at V = 75 cm (knuckle height); penalises lifts from the floor or above shoulder height.

A measure of vibration severity that accounts for peak-to-average ratio (crest factor), using the fourth-power integral of weighted acceleration. Units: m/s¹·⁷⁵. More sensitive to shocks and impacts than A(8).

A documented programme for identifying, assessing, and controlling Legionella and other waterborne pathogen risks in building water systems. Required under AS/NZS 3666, UK ACOP L8 / HSG 274, and analogous legislation in most jurisdictions.

A composite thermal index accounting for air temperature, humidity, radiant heat load, and air movement. Calculated as WBGT = 0.7 × NWB + 0.2 × GT + 0.1 × DB (outdoors). The primary international index for heat stress risk assessment (ISO 7933, ACGIH TLV).

Mechanical vibration transmitted through the seat or floor to the entire body, typically from vehicles, plant, or vibrating platforms. Associated with low-back pain and spinal disorders. Assessed per ISO 2631.

The Australian OEL, set under the Work Health and Safety (WHS) Act framework. WES-TWA and WES-STEL are reviewed by Safe Work Australia and are largely aligned with ACGIH TLVs.