Occupational hygienists, industrial hygienists, OHS consultants, safety officers, and environmental health professionals. The tools assume baseline familiarity with occupational health concepts and the relevant standards; they are not designed for untrained lay use.

Students and practitioners learning a new domain will find the tools useful for checking their manual calculations, but should work through the underlying standard alongside the tool rather than treating the output as a substitute for understanding the methodology.

Yes. All tools are free to use. Registration with a valid email address is required, which allows us to track usage and maintain the service over time.

No. All calculations run in your browser. Data you enter is not transmitted to any server and is not stored or logged. If you close or refresh the page, the data is gone. This applies to all tools.

Exactus Labs is a specialist tools project built by an occupational health and hygiene professional with a background in industrial hygiene practice. The goal is to reduce the time practitioners spend rebuilding the same spreadsheets and reduce the quiet errors that accumulate when those spreadsheets are copied between jobs.

A few common reasons:

Different standards. Many calculations exist in multiple versions (OSHA, NIOSH, ACGIH, Safe Work Australia), and they use different exchange rates, criterion levels, or reference periods. Check which standard your spreadsheet implements.

Rounding. Rounding differences accumulate across multi-step calculations, particularly for logarithmic noise calculations. Exactus Labs tools carry full precision throughout and round only at the final output stage.

Standard revision. The tool may implement a more recent version of a standard than your spreadsheet. Each tool page states the exact standard and revision it implements.

If none of these explain the discrepancy, email info@exactuslabs.com with the inputs, your result, and the standard you are using.

These tools are calculation aids. Outputs can support your professional assessment but are not a substitute for it. Whether a result is appropriate for regulatory purposes depends on your jurisdiction, the standard your regulator requires, and your professional judgement.

Validate outputs against your measurements and site conditions before relying on them in formal documentation. Each tool states the validity limits of the calculation; work within those limits.

Where standards disagree on a material point (exchange rates, criterion levels, threshold values), the tool reports all of them rather than choosing silently. This is deliberate. Picking one without disclosure is how spreadsheet errors go unnoticed for years.

The displayed results make the disagreement visible. If your jurisdiction or client requires a specific standard, use that column; but seeing the others lets you understand the margin.

Dose is a dimensionless percentage: 100% means the worker has received the full permissible daily exposure. TWA (time-weighted average) is the equivalent continuous sound level over an 8-hour reference period, expressed in dB(A). They represent the same exposure in different units: dose is better for compliance checks (is it over 100%?), TWA is better for comparison to OELs expressed in dB(A).

The mathematical relationship between them depends on the criterion level and exchange rate used by the relevant standard.

These bodies use different exchange rates and criterion levels, which produce genuinely different numbers from identical inputs.

OSHA uses a 5 dB exchange rate (a doubling of dose for every 5 dB increase) and a 90 dB(A) criterion level. NIOSH and ACGIH both use a 3 dB exchange rate and an 85 dB(A) criterion level. The 3 dB rate is based on equal energy principles and is considered more protective. The 5 dB rate reflects a regulatory compromise from 1971 that has not been revised.

The difference is not a calculation error; it reflects a genuine and long-standing regulatory disagreement. The tool reports all three so you can see which is most stringent for your scenario.

The tool uses the SNR (Single Number Rating) or SLC80 method depending on the standard selected. It calculates the protected exposure level by subtracting an adjusted attenuation value from the measured A-weighted or C-weighted level, then compares that to the relevant OEL.

The adequacy result tells you whether the protector provides sufficient attenuation for the measured environment, not whether it is being worn correctly or achieving rated attenuation in practice. Real-world attenuation is typically lower than rated values due to fit, hygiene, and compliance factors.

Enter WBGT directly if you have an instrument that measures and reports WBGT directly. The instrument's globe thermometer captures the solar radiation load, so no further correction is needed.

Measured temperatures (Tnwb + Tg + Tdb) if you have a psychrometric wet bulb, globe, and dry bulb thermometer separately. The tool applies the ACGIH formula to compute WBGT from those components, using the indoor/shade or outdoor/sun formula as selected.

Estimate from met data if you have no on-site instruments and only standard meteorological data (dry bulb temperature, relative humidity, wind speed). The tool estimates the psychrometric wet bulb and, for outdoor sun conditions, computes globe temperature using a sphere energy balance model (Liljegren 2008) with clear-sky solar irradiance. Measured instruments are always preferred; this mode is for planning or retrospective assessment.

They should not differ — the tool uses ACGIH Table 3 as the primary TLV source for both acclimatised and unacclimatised workers. The TLV card shows the Table 3 threshold for the selected work allocation, metabolic rate, and acclimatisation status. The Action Limit is derived separately from the ACGIH formula (AL = 60.0 − 14.1 × log₁₀M) and capped at the TLV.

If you see a discrepancy, check that the work allocation and metabolic rate dropdowns match what you intended. The highlighted cell in the Table 3 grid shows your current selection.

A Similar Exposure Group is a group of workers whose exposures are similar enough in source, path, and duration that a sample from part of the group can be used to characterise the whole group's exposure distribution. The concept is central to the AIHA exposure assessment framework.

Defining SEGs correctly, before sampling, is the most important step in any exposure assessment program. The Exposure Profiler analyses data at the SEG level and assumes the data you enter represents a valid SEG.

Both methods estimate the same underlying lognormal exposure distribution, but they handle uncertainty differently.

The frequentist method (maximum likelihood estimation) gives point estimates of the geometric mean and geometric standard deviation. It is straightforward but provides no direct measure of uncertainty in those estimates.

The Bayesian method incorporates prior information about plausible industrial hygiene exposure distributions and produces full credible intervals on the parameters. This is particularly useful when sample sizes are small (fewer than six samples), where frequentist point estimates can be highly unstable.

The AIHA IHSTAT methodology recommends the Bayesian approach as default, especially for small datasets. The Exposure Profiler runs both and presents both sets of results.

The exceedance fraction is the estimated proportion of the SEG's daily exposures that exceed the OEL, expressed as a percentage. A result of 5% means an estimated 5 in 100 working days would produce an exposure above the limit.

The AIHA risk band classification uses the 95th percentile credible interval of the exceedance fraction (not the point estimate) to assign the SEG to a risk band from 0 (clearly acceptable) to 4 (clearly unacceptable). Using the upper confidence bound rather than the point estimate makes the classification conservative, which is appropriate given the consequences of under-estimating exposure risk.

Control Banding is a qualitative risk assessment method used when quantitative exposure data is unavailable or impractical to obtain. The tool classifies a substance into a hazard band based on its health hazard classification and volatility or dustiness, then assigns a control approach (ranging from general ventilation to engineering containment or specialist advice) based on the estimated exposure potential.

The output is a recommended control category, not a measured or modelled concentration. It is appropriate for prioritising controls or screening substances before quantitative assessment, not as a substitute for measurement-based compliance assessment.

The tool combines individual uncertainty components (sampling pump flow rate, sampling volume, analytical recovery, method precision, and others) using the ISO GUM (Guide to the Expression of Uncertainty in Measurement) framework. Each component is expressed as a standard uncertainty, then combined in quadrature to give the combined standard uncertainty. Multiplying by a coverage factor k gives the expanded uncertainty at the chosen confidence level.

The result is expressed as a percentage of the measured value. This can be used to assess whether the uncertainty band around a measurement crosses a regulatory limit, which affects the compliance decision.

The classifier uses the WHO Laboratory Biosafety Manual (4th edition, 2020) risk group framework, which categorises microorganisms into four risk groups based on pathogenicity, transmissibility, host range, availability of effective prophylaxis or treatment, and route of exposure. The tool maps risk group to containment level and flags relevant precautions.

Classification outputs are for planning and guidance purposes. Formal biological risk assessment requires a qualified biosafety professional and must account for site-specific factors not captured by the risk group alone.

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No. Email addresses collected at registration are used only for account authentication and service communications. They are not sold, licensed, or shared with third parties.

The initial suite of 15 tools across Physical Agents, Chemical Agents, Biological Agents, and Analytics is now complete. Future additions are evaluated based on practitioner demand and whether the underlying methodology is sufficiently well-defined to implement reliably.

The tools directory shows everything currently available.

Yes. Email info@exactuslabs.com with a description of the calculation you need, the standard it should implement, and why existing solutions fall short. Priority is based on breadth of practitioner need and whether the calculation is well-defined enough to implement without ambiguity.

Email info@exactuslabs.com with the tool name, the inputs you used, the result you got, what you expected, and the standard clause you are referencing. Accuracy reports are treated seriously and investigated promptly. If the tool is wrong, it gets corrected and the change is noted.