Industrial Hygiene

  • Prevent Occupational Illnesses and Diseases by reducing/eliminating health hazard
  • Significant cost savings by reducing/recovering dust/vapor emission
  • Pollution Control at source
  • Regulations
  • Increased Productivity


  • Dust/Fume
  • Noise
  • Heat Stress
  • Ergonomics-Manual Handling

Hazard - Risk

Hazard (IPA, Lead) + Exposure = Risk

Hazard + good controls (Local Exhaust Ventilation System) < Risk

  • Industrial Hygiene - Methodology
    • Health Hazard Identification
    • Exposure/Risk Assessment
    • Controls:
    • Substitution
    • Process Changes
    • Engineering Controls
    • Administrative Controls
    • PPE/RPE
  • Phase: I- Qualitative Exposure Assessment
    • Risk Assessment/Walk Through Survey
    • Identify Hazards
    • Identify Risk
  • Phase: II- Quantitative Exposure Assessment
    • Evaluation of hazards
    • Evaluation of controls for their effectiveness

Quantitative Exposure Assessment

  • Evaluation of Hazards:
    • Air Monitoring
    • Noise Monitoring
    • Heat Stress Monitoring
  • Evaluation of Controls
    • Repeat Air, Noise and Heat Stress Monitoring after implementation of controls
    • Velocity Measurement

Air Monitoring

O Performed to identify the concentration of contaminant in the air
O Personal/Breathing Zone Air Monitoring- To identify personal exposure of the employee
O General Area Monitoring- To identify contamination in the area, efficiency of control measure

Personal Air Monitoring:

O Sampling media is placed in the breathing zone of the employee
O Best available method as it identifies individual exposure with ± 5% accuracy
O The only method approved for compliance purpose

Area Monitoring:

O Similar methodology as personal air monitoring- Sampling media is placed in the area instead of breathing zone
O Instant monitoring-Drager Tubes/Pumps Accuracy ±35%
O Fixed monitors-Great to identify areas of concerns if calibrated and lower limit is set adequately


  • Air Sampling pumps
  • Sampling Media
  • Calibrator
  • Charger
  • Air Sampling Accessories
    • Tubing
    • Cyclone
    • Flow reducers
    • Connectors
    • Labels

Air Sampling Strategy

O Air Sampling and Analytical Methods
O Where to sample
O Whom to sample
O When to sample
O How long to sample
O How many samples to take

Sampling and Analytical Method

O Identify compound with low threshold limit value and higher toxicity, Inadequate controls while handling
O Identify National Institute for Occupational Safety and Health (NIOSH) sampling and analytical methods
O National Institute for Occupational Safety and Health
O Determine sampling media (charcoal tubes, filters), flow rates, sample volumes, interferences, sample stability storage and shipping requirements

Pre Sampling Procedure:

O Calibration of Air Sampling Instrument
O Labeling of Sampling MediaO Ensure the proper connections in the sampling chain
O Explain the employee about the need of personal air monitoring function of instrument and to perform the work as a normal
O Note down information about the employee and activity to be sampled
O Start the Air sampling instrument

Blank Sample:

O To identify contamination of sampling media (if any) during the shipping and during handling by industrial hygienist
O Blank sample is collected same way as other samples except air is not passed through the sampling media
O One blank for set of six samples is recommended

During Air Monitoring..

O Observe the activities
O Note down variation in activity if any
O Ensure the Air Sampling Instrument is working

Post sampling procedures

O Remove sampling pump, media
O Cap the media
O Note down activities on that day- abnormalities, if any (e.g., spill, leak)
O Post calibrate the flow rate
O Record all data in chain of custody form
O Ship the samples to the analytical laboratory

Chain of Custody

O Important document
O Should be sent to the laboratory along with samples to be analyzed
O Confidentiality should be maintained - facility information should not go to the laboratory
O Will provide detail information about the sampling strategy and activities during sampling
O Air Sampling Forms

Analysis of Samples

O Considering the baseline data, it is preferable to analyze the samples at American Industrial Hygiene Association (AIHA)     accredited laboratory
O Accuracy and experience is higher in AIHA accredited than the laboratories in India in analysis of Industrial Hygiene Samples
O Cost of analysis is almost same as that in India
O In-house expertise can be developed for analysis of samples from all site
O Detailed methodology for analysis ( NIOSH) is available

Standards for Personal Exposure

O Threshold Limit Values (TLV, 8-hr time weighted average exposure limits)
O Short Term Exposure Limits (STEL, 15 minute exposure limits)
O Sampling strategy to identify long term (closed to 8 hours) and short term exposures employee exposures

Exposure Limits

O Sources:

  • MSDSs- Not all MSDSs will give the information about the Exposure Limits
  • Regulatory requirement- The Indian Factories Act- Exposure Limits specified for about 180 chemicals
  • NIOSH Database

O Exposure Limits not defined for about 70 % of the chemicals
O Research is not as fast as the new chemicals are coming into use
O Chemicals for which Exposure Limits are not defined but they are having high toxicity, try to reduce the     exposures to as low as feasible


O Results discussed with senior management
O Communication package containing results and interpretation of results prepared
O Communicate within five days to specific employees
O Communicated to occupational physician for medical surveillance and biological monitoring, if needed

Chain of Custody – Noise

A Details regarding the activities performed and the conditions during personal noise monitoring is important to compare the conditions while monitoring

Noise Levels – Exposure Limits
Exposure Time (Hours)
Factories Act (dBA)


O The instrument stores and displays temperature data
O It warns the user of temperatures which exceed a pre-set level via a small speaker mounted just outside the ear

Hazard Prevention and Control-Principles

O Substitution
O Engineering Controls
O Process Modification
O Ventilation
O Administrative Controls

  • Site Safety and Health Plan/Site Controls
  • Housekeeping
  • Safe Operating Procedures
  • Confined Space Entry Permit System
  • Lockout/tagout

O Personal Protective Equipment


O Local Exhaust Ventilation
O Dilution Ventilation
O Principles of Ventilation

  • Exhaust air from lab outdoors and do not recycle
  • Maintain always negative air pressure in the lab with respect to rest of the building
  • Avoid contamination of incoming air with exhaust air
  • Laminar flow of incoming air is preferable

O Definitions

  • Velocity (V)
  • Cross Sectional Area (A)
  • Volumetric Flow Rate (Q) = V x A

O Key Components of LEV

  • Exhaust Hood
  • Duct Work, Fan

O Laboratory Hood Design

  • Locate hood away from traffic, aisles and doorway
  • Locate Fan outside the Building
  • Dedicated Exhaust System
  • Avoid re-circulation of exhaust air in the building. Ensure that fans do not rotate backward
  • Exhaust air discharge to be in a vertical direction at least 10' above the adjacent roof line (ANSI/AIHA Z9.5 1992) and discharge velocity of 2000 to 3000 fpm

Velocity Measurement

  • Required for,
  • Laboratory Fume Hood
  • Local Exhaust Ventilation



*Remove contaminants by passing breathing air through a purifying element, like a filter.


A) Particulate : Uses a filter element
B) Gas and Vapor : Uses

Chemical sorbents contained in a cartridge or canister

Maharshi Mehta is Certified Industrial Hygienist from American Board of Industrial Hygiene and , Certified Safety Professional from the Board of Certified Safety Professional of America, with Master’s degree in Occupational Safety from University of Cincinnati. He has been providing industrial hygiene and safety services to more than 300 workplaces in 15 countries. He is also assisting India’s first Master in Industrial Hygiene (MIH) program.