1. Control of Work Environment Hazards
Carlos M. Cortes, Jr.
Supervising Industrial Hygienist
Environment Control Division – OSHC, DOLE

2. Work Environment Control
Measures which aim to eliminate or reduce exposure of workers to potential work environment hazards.

3. 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.

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

5. Generalized Diagram of
Methods of Control
AIR PATH
SOURCE
RECEIVER

6. General Environment Control Measures
Engineering control
Administrative control
Use of Personal Protective Equipment

7. Engineering Control Adequate Planning and Design
Substitution of Materials Used
Modification of the Process
Isolation or Shielding
Ventilation

8. 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

9. Substitution of Materials Used
Factors to be considered:
Technological and economical feasibility
Availability of substitute material
Toxicological and safety aspect

10. 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

11. 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

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

13. Purpose To ensure conditions of thermal comfort
To dilute airborne contaminants to acceptable levels
To prevent hazardous air contaminants from dispersing into the working environment

14. Types of Industrial Ventilation
General Ventilation (GV)
Local Exhaust Ventilation (LEV)

15. 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.

16. General or Dilution Ventilation
2. Mechanical Ventilation
1. Natural Ventilation
Preferred if significant health hazards exist

17. Operators Breathing Zone
Zone of Contaminant Release
Operators Breathing Zone
Clean Air Supply
Discharge Opening
Direction of air flow must remove contaminants from workers breathing zone

18. 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

19. Short Circuiting

20. 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

21. Local Exhaust Ventilation (LEV)
Removes airborne contaminants at the point of dispersion or generation before they become fugitive and contaminate the work environment.

22. LOCAL EXHAUST VENTILATION SYSTEM
Duct
Air Cleaning Device
Hoods
Fan

23. Local Exhaust Ventilation
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

24. Classification of Hoods
Enclosure type
Exterior type
Receiving type

25. Enclosure

26. 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)

27. 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.

28. 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.

29. OSHS Rule 1093. Ventilation and Exhaust Equipment
Ventilation and exhaust equipment shall be tested periodically for safe and efficient operational performance.

30. Acceptable Comfort Air Motion at the Worker
Continuous Exposure
Air Velocity, m/s
Air Conditioned workareas
General Ventilation for work stations
(Spot cooling) Sitting
Standing
0.25 – 0.375
0.375 – 0.625
0.50 – 1.0
Intermittent Exposure, Spot Cooling
Light heat loads & activity
Moderate loads & activity
High loads & activity
5-10
10-15
15-20
* Industrial Ventilation – A Manual of Recommended Practices, published by the American Conference of Governmental Industrial Hygienists.

31. Range of Capture Velocities
Condition of Contaminant Dispersion
Examples
Capture Velocity, m/s
Released with practically no velocity into quiet air
Evaporation from tanks, degreasing, etc.
Released at low velocity into moderately still air
Spray booths, welding, plating, pickling container filling, conveyor loading
Active generation into zone of rapid air motion
Spray painting in shallow booths, crushers, conveyor loading
1.0 – 2.5
Released at high initial velocity into zone of very rapid air motion
Grinding, abrasive blasting etc.
2.5 – 10.0

32. Control Velocity for Organic Solvents
Type of Hood
Air Velocity (m/s)
Enclosure Type Hood
0.4
Outside Fitted Type Hood
Side Suction Type
0.5
Bottom Suction Type
Overhead Suction Type
1.0
* Guide for Periodic Inspection of Local Exhaust Ventilation Systems
Labour Standards Bureau, Ministry of Labor, Japan

33. Control Velocity of Dust Emission Sources
Type of Hood
Air Velocity (m/s)
Enclosure Type Hood
0.7
Outside Fitted Type Hood
Side Suction Type
1.0
Bottom Suction Type
Overhead Suction Type
1.2
* Guide for Periodic Inspection of Local Exhaust Ventilation Systems
Labour Standards Bureau, Ministry of Labor, Japan

34. Administrative Control
1. Reduction of work periods
2. Adjusting work schedules
3. Employee information and training
4. Job Rotation
5. Education of supervisors

35. 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

36. 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

37. Summary 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

38. Thank You!