Control of Work Environment Hazards
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Control of Work Environment Hazards. Carlos M. Cortes, Jr. Supervising Industrial Hygienist Environment Control Division – OSHC, DOLE. Work Environment Control. Measures which aim to eliminate or reduce exposure of workers to potential work environment hazards.

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Control of Work Environment Hazards

Carlos M. Cortes, Jr.

Supervising Industrial Hygienist

Environment Control Division – OSHC, DOLE

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Work Environment Control

Measures which aim to eliminate or reduce exposure of workers to potential work environment hazards.

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Objective in the control of hazardous substances :

To prevent or minimize exposure of workers to harmful environmental hazards which could lead to serious occupational illnesses and diseases and even death.

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“The correct recognition and careful evaluation of the hazards are extremely important and will constitute the basis of appropriate control measures”

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Generalized Diagram of

Methods of Control




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General Environment Control Measures

  • Engineering control

  • Administrative control

  • Use of Personal Protective Equipment

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Engineering Control

  • Adequate Planning and Design

  • Substitution of Materials Used

  • Modification of the Process

  • Isolation or Shielding

  • Ventilation

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Adequate Planning and Design

  • The health and safety aspect should be included in the;

  • Design stage of a process

  • Selection of process equipment

  • and materials

  • Installation of equipment

  • Construction of the plant

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Substitution of Materials Used

Factors to be considered:

  • Technological and economical feasibility

  • Availability of substitute material

  • Toxicological and safety aspect

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Modification in the Process or Equipment

  • Reduces contaminant generation

  • Eliminate the formation of undesirable by-products

  • Eliminate or minimize physical contact between workers and hazardous substances

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Isolation or Shielding

  • Closed system – used for toxic chemicals

  • Enclosures – total or partial usually combined with local exhaust ventilation

  • Separating Walls – if there are operations more hazardous than the others

  • Distance – hazardous operations performed at distant locations

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  • The process of supplying or removing air by natural or mechanical means to and from any space.

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  • To ensure conditions of thermal comfort

  • To dilute airborne contaminants to acceptable levels

  • To prevent hazardous air contaminants from dispersing into the working environment

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Types of Industrial Ventilation

  • General Ventilation (GV)

  • Local Exhaust Ventilation (LEV)

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General Ventilation

  • Supply and exhaust (or remove) air in the work environment such that airborne contaminants are diluted to levels considered to be not harmful to health.

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General or Dilution Ventilation

2. Mechanical Ventilation

1. Natural Ventilation

Preferred if significant health hazards exist

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Zone of Contaminant Release

Operators Breathing Zone

Clean Air Supply

Discharge Opening

Direction of air flow must remove contaminants from workers breathing zone

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Pointers on the Use of Industrial Ventilation

Air removed must be replaced by supply air

Short circuiting of air must be prevented

Lay-out of equipment and process should be considered in relation to the direction of air flow

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Pointers on the Use of Industrial Ventilation

Avoid cross drafts of air near exhaust outlets

Contaminated air must be correctly discharged outdoors such that its re-entry inside the work environment is avoided

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Local Exhaust Ventilation (LEV)

Removes airborne contaminants at the point of dispersion or generation before they become fugitive and contaminate the work environment.

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Air Cleaning Device



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Pointers in

Local Exhaust Ventilation

  • Enclose the contaminant

  • Capture contaminant with adequate air velocities

  • Keep contaminant out of the worker’s breathing zone

  • Discharge contaminated air outdoors

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Classification of Hoods

  • Enclosure type

  • Exterior type

  • Receiving type

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Importance of Testing Ventilation Systems

1. Acceptance tests, conforming with system specs

2. Compliance to safety and health regulations

3. Determining appropriate air velocities

4. Providing recommendations for the purpose of protecting workers (from exposure to hazardous contaminants)

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OSHS Rule 1076. General Ventilation

Air Supply:

Clean fresh air shall be supplied to enclosed workplaces at an average rate of not less than 20 to 40 cu.m. (700 to 1400 cu.ft.) an hour per worker for a complete air change from 4 to 8 per hour.

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OSHS Rule 1076. General Ventilation (con’t)

Air Movement:

The air movement in enclosed workplaces shall be arranged such that workers are not subjected to objectionable drafts. Air velocity shall range from 0.25 m/s to 0.75 m/s during rainy and summer season, respectively.

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OSHS Rule 1093. Ventilation and Exhaust Equipment

Ventilation and exhaust equipment shall be tested periodically for safe and efficient operational performance.

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Acceptable Comfort Air Motion at the Worker

* Industrial Ventilation – A Manual of Recommended Practices, published by the American Conference of Governmental Industrial Hygienists.

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Control Velocity for Organic Solvents

* Guide for Periodic Inspection of Local Exhaust Ventilation Systems

Labour Standards Bureau, Ministry of Labor, Japan

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Control Velocity of Dust Emission Sources

* Guide for Periodic Inspection of Local Exhaust Ventilation Systems

Labour Standards Bureau, Ministry of Labor, Japan

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Administrative Control

1. Reduction of work periods

2. Adjusting work schedules

3. Employee information and training

4. Job Rotation

5. Education of supervisors

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Respiratory Protective Equipment

Should not be regarded as the first line of defense or as a primary means to control hazards but rather as a supplement to other types of measures

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Criteria for Selection

of Respirators

  • Identification of contaminants

  • Maximum possible concentration of contaminants in the workarea

  • Acceptability in terms of comfort

  • Compatibility with the nature of job

  • Proper fit to the face of user to prevent leakage

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  • Importance of 3 A’s in Industrial Hygiene

  • Engineering control as the primary means

  • Administrative control as a supplement

  • PPEs as the last line of defense