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.
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.
“The correct recognition and
careful evaluation of the hazards
are extremely important and will
constitute the basis of appropriate
control measures”
Generalized Diagram of
Methods of Control
SOURCE AIR PATH RECEIVER
General Environment Control
Measures
1. Engineering control
2. Administrative control
3. Use of Personal Protective
Equipment
Engineering Control
1. Adequate Planning and Design
2. Substitution of Materials Used
3. Modification of the Process
4. Isolation or Shielding
5. Ventilation
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
Substitution of Materials Used
Factors to be considered:
Technological and economical feasibility
Availability of substitute material
Toxicological and safety aspect
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
Isolation or Shielding
a) Closed system – used for toxic chemicals
b) Enclosures – total or partial usually combined with
local exhaust ventilation
c) Separating Walls – if there are operations more
hazardous than the others
d) Distance – hazardous operations performed at
distant locations
Ventilation
The process of supplying or
removing air by natural or
mechanical means to and from any
space.
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
Types of Industrial Ventilation
• General Ventilation (GV)
• Local Exhaust Ventilation (LEV)
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.
General or Dilution Ventilation
1. Natural 2. Mechanical
Ventilation Ventilation
Preferred if significant
health hazards exist
Zone of
Contaminant
Release Operators Breathing
Zone Clean Air
Discharge Supply
Opening
Direction of air flow must remove contaminants from
workers breathing zone
Pointers on the Use of Industrial
Ventilation
1. Air removed must be replaced by supply air
2. Short circuiting of air must be prevented
3. Lay-out of equipment and process should
be considered in relation to the direction of
air flow
Short Circuiting
Pointers on the Use of
Industrial Ventilation
4. Avoid cross drafts of air near exhaust
outlets
5. Contaminated air must be correctly
discharged outdoors such that its re-entry
inside the work environment is avoided
Local Exhaust Ventilation (LEV)
Removes airborne contaminants at the
point of dispersion or generation
before they become fugitive and
contaminate the work environment.
LOCAL EXHAUST
VENTILATION SYSTEM
Duct
Air Cleaning Device
Hoods Fan
Pointers in
Local Exhaust Ventilation
1. Enclose the contaminant
2. Capture contaminant with
adequate air velocities
3. Keep contaminant out of the
worker’s breathing zone
4. Discharge contaminated air
outdoors
Classification of Hoods
1. Enclosure type
2. Exterior type
3. Receiving type
Enclosure
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)
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.
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.
OSHS Rule 1093.
Ventilation and Exhaust
Equipment
Ventilation and exhaust equipment shall
be tested periodically for safe and
efficient operational performance.
Acceptable Comfort Air Motion
at the Worker
Continuous Exposure Air Velocity, m/s
Air Conditioned workareas 0.25 – 0.375
General Ventilation for work stations
(Spot cooling) Sitting 0.375 – 0.625
Standing 0.50 – 1.0
Intermittent Exposure, Spot
Cooling
Light heat loads & activity 5-10
Moderate loads & activity 10-15
High loads & activity
15-20
* Industrial Ventilation – A Manual of Recommended Practices, published by the American
Conference of Governmental Industrial Hygienists.
Range of Capture Velocities
Condition of
Capture
Contaminant Examples
Velocity, m/s
Dispersion
Released with practically Evaporation from
no velocity into quiet air tanks, degreasing, 0.25 -0.5
etc.
Released at low velocity Spray booths,
into moderately still air welding, plating,
pickling container 0.5 -1.0
filling, conveyor
loading
Active generation into Spray painting in
zone of rapid air motion shallow booths,
1.0 – 2.5
crushers, conveyor
loading
Released at high initial Grinding, abrasive
velocity into zone of very blasting etc. 2.5 – 10.0
rapid air motion
Control Velocity for Organic Solvents
Type of Hood Air Velocity
(m/s)
Enclosure Type Hood 0.4
Side Suction Type 0.5
Outside Bottom Suction 0.5
Fitted Type Type
Hood Overhead Suction 1.0
Type
* Guide for Periodic Inspection of Local Exhaust Ventilation Systems
Labour Standards Bureau, Ministry of Labor, Japan
Control Velocity of Dust Emission
Sources
Type of Hood Air Velocity
(m/s)
Enclosure Type Hood 0.7
Side Suction Type 1.0
Outside Fitted Bottom Suction Type 1.0
Type Hood
Overhead Suction
Type 1.2
* Guide for Periodic Inspection of Local Exhaust Ventilation Systems
Labour Standards Bureau, Ministry of Labor, Japan
Administrative Control
1. Reduction of work periods
2. Adjusting work schedules
3. Employee information and training
4. Job Rotation
5. Education of supervisors
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
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
Summary
1. Importance of 3 A’s in Industrial
Hygiene
2. Engineering control as the primary
means
3. Administrative control as a
supplement
4. PPEs as the last line of defense
Thank You!