Occupational Hygiene Knowledge Centre
Explore practical resources on occupational hygiene, including workplace health hazard recognition, exposure assessment, air monitoring, noise monitoring, chemical exposure, dust and particulates, heat stress, indoor air quality, control measures, sampling methods, occupational exposure limits and medical surveillance requirements.
What is Occupational Hygiene?
Occupational hygiene is the discipline of anticipating, recognising, evaluating and controlling workplace health hazards. It focuses on preventing occupational illness, protecting worker health and supporting better decisions on workplace risk management.
Health hazard prevention
Occupational hygiene considers chemical, physical, biological and environmental hazards that may affect workers during routine and non-routine work.
Evidence-based workplace decisions
Exposure assessment, monitoring, control verification and professional judgement help organisations understand whether exposure is adequately controlled.
Long-term health protection
Effective occupational hygiene supports compliance, risk management, health surveillance, worker confidence and prevention of occupational illness.
Explore key occupational hygiene topics
Use the tabs below to switch between key occupational hygiene topics. Each section summarises what the topic covers, why it matters, common workplace issues and when professional support may be useful.
Occupational Hygiene Overview
Occupational hygiene follows a structured process: anticipate hazards, recognise sources of exposure, evaluate worker exposure, control risks, then review and verify whether controls remain effective.
It helps prevent occupational illness and provides a clearer basis for workplace health decisions.
Common workplace issues
Chemical vapours, dusts, noise, heat, poor ventilation, odours, biological agents and uncertain exposure levels.
What to consider
Work activities, materials used, exposure duration, routes of exposure, controls, worker groups and applicable limits.
Assessment approaches
Walkthrough surveys, SDS review, task observation, similar exposure grouping, monitoring and professional interpretation.
Control or reporting focus
IEH helps organisations understand and manage workplace health risks through practical assessment, monitoring and advisory support.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Air Monitoring
Air monitoring assesses airborne contaminants that workers may inhale, including vapours, gases, fumes, mists, fibres, dusts and particulates. Monitoring may involve personal sampling, area sampling or a combination of approaches.
Air monitoring helps determine whether airborne exposure is adequately controlled and whether further action is needed.
Common workplace issues
Solvent vapours, welding fumes, process emissions, cleaning chemicals, powders, nuisance odours and poor capture at source.
What to consider
Sampling objective, similar exposure groups, contaminant type, task duration, process variability and existing controls.
Assessment approaches
Personal exposure monitoring, area sampling, short-term task sampling, screening measurements and control verification.
Control or reporting focus
Results should be interpreted against relevant reference values, work context, sampling limitations and practical controls.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Noise Monitoring
Noise monitoring helps organisations understand occupational noise exposure, identify noisy areas or activities, and support hearing conservation planning.
Excessive noise exposure can contribute to noise-induced hearing loss and may require control, monitoring and health surveillance measures.
Common workplace issues
Machinery noise, compressed air, impact noise, production lines, workshops, maintenance tasks and process equipment.
What to consider
Worker exposure pattern, task duration, noise variability, peak noise, shift length, existing controls and hearing protection use.
Assessment approaches
Personal noise dosimetry, area noise measurement, noise mapping and task-based measurements where appropriate.
Control or reporting focus
Engineering noise reduction, enclosure, isolation, maintenance, administrative controls and suitable hearing protection.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Chemical Exposure
Chemical exposure assessment considers how hazardous substances may enter the body through inhalation, skin contact, ingestion or injection, and whether current controls are adequate.
Chemicals may cause acute effects, chronic disease, irritation, sensitisation, reproductive harm or systemic toxicity depending on exposure.
Common workplace issues
Solvents, acids, alkalis, cleaning agents, adhesives, resins, laboratory reagents, process chemicals and maintenance chemicals.
What to consider
SDS information, chemical inventory, hazard classification, exposure routes, quantities used, task frequency and worker groups.
Assessment approaches
SDS review, exposure screening, air monitoring, dermal exposure review, ventilation assessment and PPE suitability review.
Control or reporting focus
Substitution, closed systems, local exhaust ventilation, containment, safe work procedures, hygiene facilities and suitable PPE.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Dust and Particulates
Dust exposure assessment considers airborne particulates generated by handling, transfer, cutting, grinding, mixing, blasting, cleaning, packaging or other dust-generating activities.
Dust exposure may affect respiratory health, visibility, housekeeping, combustible dust risk and general workplace hygiene.
Common workplace issues
Total dust, inhalable dust, respirable dust, silica-containing dust, powders, fibres, nuisance dust and settled dust accumulation.
What to consider
Particle size fraction, material composition, process conditions, worker proximity, exposure duration and control effectiveness.
Assessment approaches
Personal sampling, area sampling, task-based sampling, similar exposure group planning and laboratory analysis where required.
Control or reporting focus
Enclosure, local exhaust ventilation, wet methods, process isolation, housekeeping, vacuum systems and respiratory protection.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Heat Stress
Heat stress assessment considers environmental heat, metabolic workload, clothing, PPE, acclimatisation, hydration and work organisation.
Heat stress can affect comfort, concentration, productivity and safety, and may contribute to heat-related illness.
Common workplace issues
Outdoor work, hot processes, kitchens, laundries, foundries, boiler rooms, confined spaces and heavy physical work.
What to consider
WBGT, workload, radiant heat, air movement, humidity, clothing, PPE, worker fitness and acclimatisation status.
Assessment approaches
Heat stress screening, WBGT monitoring, workload estimation, task observation and review of work-rest arrangements.
Control or reporting focus
Work-rest planning, hydration, shade, cooling, ventilation, scheduling, acclimatisation and emergency response planning.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Indoor Air Quality
Indoor air quality investigation considers occupant complaints, ventilation, comfort parameters, airborne contaminants, odours and possible building-related symptoms.
Good indoor air quality supports comfort, wellbeing, productivity and confidence in workplace facilities.
Common workplace issues
Temperature, humidity, carbon dioxide, VOCs, particulates, odours, mould concerns, water damage and poor ventilation.
What to consider
Complaint pattern, building layout, occupancy, ventilation system, renovation works, nearby sources and maintenance records.
Assessment approaches
Walkthrough inspection, occupant interviews, ventilation review, comfort measurements and targeted monitoring where appropriate.
Control or reporting focus
Ventilation improvement, source removal, housekeeping, moisture control, maintenance and communication with occupants.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Biological Hazards
Biological hazard assessment considers exposure to biological agents or materials that may arise from people, animals, waste, water systems, organic dusts, mould, healthcare work or laboratory activities.
Biological agents may cause infection, allergy, irritation or sensitisation depending on the hazard and exposure route.
Common workplace issues
Mould, bacteria, organic dusts, waste handling, wastewater work, healthcare settings, laboratories and cleaning activities.
What to consider
Source of biological material, route of exposure, task frequency, vulnerable workers, hygiene practices and control barriers.
Assessment approaches
Walkthrough review, task observation, hygiene assessment, moisture investigation and targeted sampling where justified.
Control or reporting focus
Containment, hygiene facilities, cleaning, disinfection, safe waste handling, training, PPE and exposure control procedures.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Control Measures
Occupational hygiene control measures should follow the hierarchy of controls, with preference for eliminating or reducing exposure at source before relying on administrative controls or PPE.
Monitoring without practical control action rarely improves workplace health. Effective controls reduce exposure and prevent illness.
Common workplace issues
Over-reliance on PPE, poor ventilation, uncontrolled emissions, inconsistent procedures and lack of control verification.
What to consider
Hazard severity, exposure route, feasibility, worker acceptance, maintenance needs and whether controls remain effective.
Assessment approaches
Elimination, substitution, enclosure, isolation, local exhaust ventilation, process change and automation where suitable.
Control or reporting focus
Safe work procedures, training, supervision, work scheduling, housekeeping, hygiene facilities and PPE programmes.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Sampling and Analytical Methods
Sampling and analytical methods should be selected based on the contaminant, sampling objective, expected concentration, exposure pattern, available method guidance and laboratory requirements.
Reliable sampling supports credible results. Poor method selection may lead to misleading or unusable findings.
Common workplace issues
Wrong sampling media, unsuitable flow rate, short sampling duration, poor documentation and unclear interpretation limits.
What to consider
Sampling media, flow rate, duration, calibration, field blanks, laboratory analysis, detection limits and quality assurance.
Assessment approaches
Recognised methods may include NIOSH, OSHA, HSE or other suitable occupational hygiene methods where appropriate.
Control or reporting focus
Results should be read with the sampling strategy, exposure variability, method limitations and work context in mind.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Occupational Exposure Limits
Occupational exposure limits are reference values used to support exposure assessment and risk management. They may include time-weighted averages, short-term exposure limits or ceiling limits.
Exposure limits help organisations interpret monitoring results and prioritise control measures, where applicable limits exist.
Common workplace issues
Misreading units, comparing the wrong averaging period, overlooking mixtures and treating limits as the only safety benchmark.
What to consider
Time-weighted average, short-term exposure, ceiling values, sampling duration, exposure pattern and worker susceptibility.
Assessment approaches
Relevant Singapore permissible exposure levels may be considered where applicable, alongside suitable professional guidance.
Control or reporting focus
Results should be interpreted with uncertainty, exposure variability, control reliability and health risk context in mind.
When to seek support
Seek professional support when exposure is uncertain, complaints arise, controls need verification, or regulatory, client or audit expectations require evidence.
Practical output
A useful review should provide clear findings, limitations, risk-based interpretation and practical next actions for management.
Practical tools and checklists
Use these IEH tools, guides and checklists to support occupational hygiene planning, exposure assessment, sampling strategy, interpretation of exposure limits and preparation for professional monitoring.
Singapore PEL Lookup Tool
Quickly check Singapore Permissible Exposure Levels for listed toxic substances, including substance names, CAS numbers, long-term values and short-term values where available.
Medical Examination Schedule Lookup Tool
Review prescribed medical examinations, pre-placement examination requirements and periodic examination frequencies for selected occupational exposures.
Air Sampling Guidelines
Access practical guidance to support occupational hygiene air sampling planning in Singapore, including sampling objectives, workplace information, exposure groups and monitoring considerations.
Chemical Sampling and Analytical Methods
Use IEH’s practical occupational hygiene tool to support chemical sampling method selection, including recognised method references, sampling media, analytical techniques and field planning considerations.
PPM to mg/m³ Converter
Convert between parts per million and mg/m³ for gases and vapours, using molecular weight and relevant assumptions.
Noise Exposure Calculator
Estimate daily noise exposure using task sound levels and exposure durations as an initial screening aid.
Air Monitoring Planning Checklist
Prepare information on contaminants, processes, worker groups, task duration, sampling objectives and controls.
Chemical Exposure Screening Checklist
Review SDS details, exposure routes, quantities used, frequency of use, ventilation, PPE and existing controls.
Dust Sampling Planner
Identify dust-generating tasks, dust fractions of interest, exposure groups, sampling duration and control measures.
Heat Stress Screening Tool
Screen hot work conditions by considering environment, workload, clothing, hydration, acclimatisation and work-rest planning.
IAQ Complaint Screening Checklist
Collect complaint patterns, location, timing, occupancy, ventilation, odour sources and recent building changes.
Occupational Hygiene Survey Planning Checklist
Organise workplace information before an occupational hygiene walkthrough, survey or exposure monitoring project.
Exposure assessment approach
Occupational hygiene assessment should be proportionate to the workplace, hazard, task and purpose of the study. A suitable approach may include selected elements from the steps below.
Workplace walkthrough and process review
Understand work activities, materials, equipment, task sequence, exposure sources and existing controls.
SDS and chemical inventory review
Review hazardous substances, physical forms, routes of exposure, health hazards and relevant handling information.
Similar exposure grouping
Group workers with comparable tasks and exposure profiles to support representative exposure assessment.
Worker interviews and task observations
Understand real work practices, non-routine activities, duration, frequency, complaints and practical constraints.
Personal and area exposure monitoring
Conduct monitoring where appropriate to assess personal exposure, background levels, source contribution or control performance.
Professional interpretation
Interpret findings against suitable reference values, sampling limitations and exposure variability, then provide practical recommendations.
Standards and references
Occupational hygiene work may refer to regulatory requirements, recognised guidance and established sampling or analytical methods. The specific references used should depend on the hazard, project objective, workplace context and jurisdiction.
Singapore WSH requirements
Relevant workplace safety and health requirements may guide employer duties, risk management, monitoring needs and occupational health programmes.
Permissible exposure levels
Exposure limits may be used as reference values when interpreting occupational exposure monitoring results, where applicable.
Noise requirements
Occupational noise assessment may support hearing conservation planning, control measures and review of worker exposure.
Statutory medical examination
Health surveillance or medical examination requirements may be relevant for selected hazards, depending on the workplace and exposure profile.
Sampling and analytical methods
Recognised occupational hygiene methods, such as NIOSH, OSHA, HSE or other suitable methods, may be used where appropriate.
Professional guidance
Guidance from occupational hygiene, regulatory or professional bodies may support sampling strategy, interpretation and control recommendations.
Designed for people managing workplace health risks
This resource is designed for people who need to understand, manage or support workplace health risk decisions.
Employers and management teams
Understand common workplace health hazards and when assessment or monitoring may be needed.
WSH professionals
Use the topic summaries and checklists to support hazard recognition, workplace inspections and risk management planning.
Occupational hygienists
Use this as a concise reference page for communicating occupational hygiene concepts to stakeholders and clients.
EHS managers
Use the assessment approach to plan monitoring programmes, control reviews and workplace health initiatives.
Facilities and operations teams
Use this resource when dealing with ventilation, IAQ, noise, heat, dust, odours or process-related exposures.
Consultants and auditors
Use this page to support preliminary review, gap identification and practical discussion with workplace stakeholders.
Frequently asked questions
These concise answers help users understand key occupational hygiene concepts and when further assessment may be required.
What is occupational hygiene?
Occupational hygiene is the discipline of anticipating, recognising, evaluating and controlling workplace health hazards to prevent occupational illness and protect worker health.
When should a company conduct occupational hygiene monitoring?
Monitoring may be needed when exposure is uncertain, hazardous substances or noisy processes are present, worker complaints arise, controls need verification, processes change or evidence is required for risk management, audit or compliance purposes.
What is the difference between personal and area sampling?
Personal sampling measures exposure close to the worker’s breathing zone or hearing zone during work. Area sampling measures contaminant or noise levels at a fixed location and is usually used to understand sources, background levels or control performance.
What is air monitoring?
Air monitoring is the measurement of airborne contaminants such as gases, vapours, fumes, mists, fibres, dusts or particulates to support exposure assessment and control decisions.
When is noise monitoring needed?
Noise monitoring may be needed when workers are exposed to loud equipment, machinery, impact noise or noisy processes, or when an organisation needs to assess occupational noise exposure and hearing conservation measures.
What are occupational exposure limits?
Occupational exposure limits are reference values used to help interpret exposure monitoring results. They may include time-weighted averages, short-term exposure limits or ceiling values, depending on the substance and reference used.
What is a similar exposure group?
A similar exposure group is a group of workers who perform similar tasks under similar conditions and are expected to have comparable exposure profiles. This helps occupational hygienists plan representative exposure assessment.
How are chemical exposure risks assessed?
Chemical exposure risks may be assessed through SDS review, chemical inventory review, task observation, exposure route assessment, control review, air monitoring, PPE review and professional interpretation of exposure information.
What should employers prepare before monitoring?
Employers should prepare process information, chemical inventories, SDS documents, work schedules, task descriptions, worker groups, existing risk assessments, control information and any previous monitoring records.
When should professional support be sought?
Professional support should be sought when exposure is uncertain, hazards are significant, monitoring is required, complaints persist, controls need verification or results require competent interpretation and practical recommendations.
Need help assessing and managing workplace health risks?
IEH supports organisations with occupational hygiene assessments, exposure monitoring, air monitoring, noise monitoring, chemical exposure assessment, heat stress assessment, indoor air quality investigation, control review and customised training.