Occupational Hygiene Tool

Semi-Quantitative Chemical Exposure Risk Assessment Tool

Screen and prioritise potential occupational exposure to harmful chemicals using a structured method based on hazard rating, vapour pressure or particle size, odour threshold ratio, exposure duration, quantity used and control effectiveness.

Start assessment View method

Reference: This tool is based on the method described in MOM’s guide, A Semi-Quantitative Method to Assess Occupational Exposure to Harmful Chemicals.

Assessment

Complete the screening form

Choose whether the chemical is in the GP-listed chemical database from the workbook, or assess another chemical of concern manually using the SDS and workplace task information.

1. Assessment pathway

GP-listed chemicalAuto-populate hazard rating, vapour pressure index, OT/PEL index and medical examination indicator from the workbook list. Other chemical of concernManually select hazard and exposure indices based on SDS and task information.

Department

Location

Process / Task

No. of potentially exposed workers

Task notes

2. Select GP-listed chemical

Chemical

The list is taken from the uploaded workbook’s ChemicalList sheet.

Particle size / solid form, if applicable

For liquids or gases, leave as “Not available / not applicable”. For solids, select the most relevant particle size or dustiness band.

Hazard Rating—

Vapour Pressure Index—

PEL—

OT / PEL Index—

OT / PEL Ratio—

Medical Examination—

2. Assess other chemical of concern

Chemical name

Health hazard description / category

Select the closest hazard category based on SDS Section 2 and available toxicological information.

Vapour pressure or particle size

Odour threshold / TLV or PEL ratio

3. Exposure and control factors

Existing hazard control measures

Duration of exposure

Amount used per week

The exposure rating is calculated as the geometric mean of the available numeric exposure indices. “Not available / not applicable” values are excluded from the geometric mean, consistent with the workbook logic.

Assessment result

Hazard Rating—

Exposure Rating—

Risk Score—

Awaiting input

Complete the form and calculate the result. The risk score is calculated as √(Hazard Rating × Exposure Rating).

No recommendation has been generated yet.

Included exposure indices—

Monitoring recommendation—

This is a preliminary semi-quantitative screening tool. It does not replace a formal chemical risk assessment, statutory compliance review, workplace exposure monitoring, medical surveillance determination or professional occupational hygiene assessment.

Method

How the tool calculates risk

The web tool preserves the workbook’s semi-quantitative logic and converts the scoring workflow into an interactive calculator.

1. Hazard Rating (HR)

For listed chemicals, HR is retrieved from the workbook chemical list. For other chemicals, HR is selected from the health hazard category table.

2. Exposure Rating (ER)

ER is the geometric mean of available numeric indices: vapour pressure or particle size, OT/PEL or OT/TLV ratio, controls, duration and amount used.

3. Risk Score

Risk Score = √(HR × ER). The score is then mapped to Negligible, Low, Medium, High or Very High risk using the workbook thresholds.

Assessment Log

Screened tasks

Add assessment results to the table for review, internal discussion or export. Results are stored only in your browser session unless you copy or export them.

Pathway	Department / Location	Process / Task	Chemical	HR	ER	Risk Score	Risk Level	Recommended Action
No assessment added yet.