niosh wpa- glomax

Report of Hazards

in the Field Operation Section of

A Ducting Contractor

By

Index No: EES1330

IC No: 761208-12-5475

Safety and Health Officer Examnimation (2/2011)

Paper IV Part 1: Workplace Assignment

16 February 2011 – 31 Mac 2011

1.0 ABSTRACT

Glo Max Engineering Sdn Bhd is a commercial air conditioning contractor. The objective of this

work place assignment was conducted to identify the health and safety risk of sheet metal duct

installers in the field; the site selected was a construction site, South China Sea Place in Kota

Kinabalu.

The hazard identification methods used are inclusive of document review, workplace inspection

and job hazard analysis (JHA). Risk assessment was done using qualitative risk table. The Risk

control hierarchy was used to make risk control recommendations. The critical risk hazards

found were safety risk of falling from height and health risk of exposure to organic solvents.

The worker feedback reviews reveals that the workers have some knowledge of safety at site,

mostly from CIBD training, but were unfamiliar with the concept of hierarchy of control. The

control method recommended were engineering controls, administrative controls and as a last

resort, PPE.

In conclusion, the installers in the company face the daily high hazards challenges typical of

workers in the construction industry.

2.0 INTRODUCTION

2.1 THE COMPANY

Glo Max Engineering Sdn Bhd is a contractor in the air conditioning business. The company is

10 years old. They are air conditioning ducting specialist based in Kota Kinabalu. The company

designs, supplies and installs sheet metal ducting of air conditioning and mechanical ventilation

systems for new buildings and building renovations. They include shopping centers, hotels,

hospitals and shop lots.

The organization chart of the company is as follows:

Director/

Project Manager

Transporter

1 Lorry Driver

Factory Operations 1 no Supervisor

2 nos Skilled Worker

3 nos General Woker

Field Operations 5 x 5 Person Teams

Team Members

1 no Supervisor

1 no Skilled Worker

3 nos General Woker

2.2 THE WORKPLACE

The scope of this WPA is study the risk of the duct installers in the field operations. This is a

critical part of the company activities as it forms the main bulk of work on site. It is also the

activity that is required to be done quickly with some incidents reported in the past. This is also

an activity with financial significance and therefore of utmost important to the operation of the

company. The workplace chosen is South China Sea Place, Kota Kinabalu that is currently

under construction.

2.3 COMPANY ACTIVITIES

The field operations of the company in the workplace includes survey and measurement of

required duct dimensions, ducting fabrication in the factory, delivery to construction site,

hoisting or manual handling to required area, duct installation, insulation of duct, installation of

grilles, testing work and cleanup work.

Below is the typical process flow of the company activities.

Figure 1. Complete Work Process for Glo Max Engineering

*The focus of this report is to identify the hazards affecting the field operations crew.

1. Site

Measurements

2. Factory

Fabrication of

Ducts

3. Field

Installation of

Ducts*

4. Onsite

Testing

The work process of Field Installation of Ducts is expanded further in Figure 2.

Figure 2: Work Processes for Field Installation of Duct

Field operation team consists of 5 persons with a supervisor as team leader in each team. The

supervisor is in charge of their overall activities. He will report to the project manager. Under

his charge will be a skilled worker with 3 general workers.

Receipt of duct sections from factory and storage

Install supporting brackets on the ceiling

Assemble duct sections and seal duct gaps

Glue and wrap fiberglass and aluminum foil to duct

Hoist and lay duct on bracket

Joint, seal and insulate duct joints

2.4 WORK ENVIRONMENT, TASK PERFORMED AND TYPICAL HAZARDS

Work Environment

The work environment of the field crew is a construction site. Work is done in designated open

area in the shade under the cover of concrete ceiling slabs. However, the conditions of the

construction site could be dusty, smoky, wet and muddy depending on the weather or clean up

works in progress. The work often is done within a limited time, often requires coordination

with others and working simultaneously with other trades in the same area. As such the crew

member could be exposed to hazards of other trades e.g. working while spray painting is in

progress.

Task Performed

Among the tasks often performed by the crew are: cutting of ducts, applying sealant to duct

joints, applying glue to insulation materials, drilling holes in the ceiling slab for hanging rods,

hammering and shaping metal sheets, hoisting or handling ducts. As the ducts are hanging from

the top of the ceiling, the installers often have to work on scaffolding or from ladders.

Typical Hazards

Typical health hazards are noise, volatile organic compound, mineral dust, disease carrying

insects, muscle strains etc.

Typical safety hazards in the work place are falling from height, falling objects, cutting hazards,

stabbing hazards, electrical and mechanical hazards.

3.0 OBJECTIVES

The objectives of this work place assignment are to:-

1.) Identify hazards that are present in workplace for the installation crew

2.) Assess the safety and health risk in this workplace

3.) Provide recommendations to control these risks

4.) Receive feedback from site staff about their health and safety concerns

5.) Propose a review system to continuously improve safety and health of workers at the

work place.

4.0 METHOD

4.1 HAZARD IDENTIFICATION

The hazards we are trying identified can be broadly categorized into the following group:-

• Safety hazards

• Biological hazards

• Chemical hazards

• Ergonomic hazards.

• Physical hazards

The methods used for hazard identification of the work place:-

1) Review of incident reports and relevant document

2) Work place inspection

3) Job hazard analysis

The following is the explanation of the methods use.

4.1.1 Review of incident reports and relevant document

The objective of this method is to identify hazards present in the work place from history of

worker illnesses and injuries, from information collected from suppliers and workers and from

industrial incident statistics. The following items were reviewed:-

I. Review Material and Chemical Safety Data Sheet

Date sheet were scrutinized to see if the recommended control measures by the

manufacturers were understood and implemented by the workers.

• MSDS and CSDS for relevant chemical were collected and analysed.

II. Review Incident Reports and Medical Records

Incidents reports were used to spot the geographical areas or processes that were

hazardous in the past 5 year

• There were 2 reported lost time injury cases of workers falling from ladders.

• There were 2 reported cases of malaria requiring treatment.

III. Review Industry Statistic Report

The most common accidents in typical work places were noted and compared to hazards

applicable to the workers. (Sosco Annual Report 2009)

4.1.2 Work Place Inspection

This method requires the physical inspection of the work place. The objective of this method is

to identify hazards in the work place by physical observation of the work place and acquiring the

feedback of workers in site. Activities include observation and survey the work place

environment, conditions and methods of use of tools and equipments, worker behavior and work

methodology. Preparation is required for efficient work. Workers and safety committee are

informed of this activity and briefed on the objectives, their individual roles and responsibilities

During the inspection, the following are the method by which the inspection was carried out:

• Inspect statistical high risk areas

This method will save time in locating hazards. In the construction site, focus

will be given to jobs where workers are exposed to ‘fall from heights’ and

‘falling objects’. (Sosco Annual Report 2009)

• Geographical on-site survey to locate troubled areas

A walk through survey exposed hazards that exist on site. The areas that had the

most activity had the most hazards.

• Work process survey

There were too many activities that happen in the field. Therefore this method is

use when specific important but hazardous work is identified. Job hazard analysis

is done for the most common activity.

4.1.3 Job hazard analysis (JHA)

This method requires the safety committee to observe the whole process of the work. The

objective is to identify the hazards in each step of the work process. The chosen work for the job

hazard analysis was decided after considering the criterias as stated below. Job hazard analysis

is important component for the preparation of Safe Work Procedures.

According to “Garis Panduan bagi Pengenalan Hazad, Penaksiran Risiko dan Kawalan Risiko”

issued by DOSH Malaysia in 2008:-

“Sometimes hazards identified cannot be eliminated or removed from some specific

activities. Safe Work Procedure is a step by step instruction allowing the worker to work

safely in the presence of hazards.”

Generally, JHA and afe Work Procedures is prepared for:-

1. Critical work with high risk

2. Hazardous work which accidents are frequent

3. New work or when there is a change in work process,

4. New equipment installed

5. Detailed work requiring constant vigilance

6. When two or more workers are required to do coordinate and work together

simultaneously

7. Special work that are seldom done.

4.2 RISK ASSESSMENT (RISK ESTIMATION AND RISK EVALUATION)

After hazards are identified, the hazards are assessed to determine the risk to the safety and

health of the workers. Risk is determined by the severity caused by the hazard and the likelihood

of it happening. Risk of a hazard can be ranked so that priority can be given to higher risk

hazards. The method used here was qualitative analysis to assess each hazard. Risk is calculated

using the following formula:-

RELATIVE RISK = SEVERITY x LIKELIHOOD

4.2.1 SEVERITY

Severity is given a scale of 1 to 5 with the higher number indicating an incident with the most

severe impact. Severity is defined in the following table:-

TABLE: SEVERITY DEFINATION

SEVERITY EXAMPLE RATE

CALAMITY Multiple fatality, massive damage of property

and production cannot be restored

5

FATALITY Estimated one dead, big damage to property 4

SERIOUS Serious non fatal injury, permanent disability 3

LIGHT Temporary disability 2

MINOR Cut, bruises, or first aid cases 1

Adapted from HIRARC Guidelines

4.2.2 LIKELIHOOD

Likelihood was given a scale to 1 to 5 with the highest number indicating an event that is most

likely to happen. The table below shows how likelihood was ranked.

TABLE: LIKELIHOOD DEFINATION

LIKELIHOOD EXAMPLE RATE

VERY

LIKELY

Incident that can happen anytime 5

LIKELY Maybe will happen, would not be unusual 4

UNLIKELY Maybe will happen in the future 3

HIGHLY

UNLIKELY

Maybe will happens once in a few years 2

UNEXPECTED Near impossible and never happened 1


4.2.2 RISK MATRIX

Risk being a product of likelihood and severity was then plotted to a matrix as shown in the

following table.

RISK MATRIX TABLE

LIKELIHOOD

SEVERITY

1 2 3 4 5

5 5 10 15 20 25

4 4 8 12 16 20

3 3 6 9 12 15

2 2 4 6 8 10

1 1 2 3 4 5


From the risk matrix above, risk can be prioritized and the required action identified.

RISK DEFINATION TABLE


RISK RISK RATING REQUIRED ACTION

15 to 25 VERY HIGH RISK Immediate action required to control the hazard as per

the risk control hierarchy. Action plan with dateline

must be included.

5 to 12 MEDIUM RISK Use a plan and systematic approach to risk control.

Temporary solution to control risk if necessary.

1 to 4 LOW RISK These risks are considered acceptable and further

reduction of risk may not be necessary. However, record

should still be kept for reference

4.3 RISK ASSESSMENT EXAMPLE

A safety and a health hazard are used to illustrate the risk assessment method used.

Safety Hazard Example

Activity: Working in a car workshop with poor housekeeping

ITEM REMARKS

Hazard Oily floors

Worst Consequence Fatal head trauma from falling down

Severity Serious non fatal injury, permanent disability [Severity rate of 3]

Likelihood Could happen anytime [Likelihood rate of 5]

Risk: from the risk

matrix

15 (Very High Risk)

Action Required Immediate action required to control the hazard as per the risk

control hierarchy. Action plan with dateline must be included.

Health Hazard Example

Activity: Working in an airport runway

ITEM REMARKS

Hazard Noise exceeding PEL

Worst Consequence Permanent deafness

Severity Serious non fatal injury, permanent disability [Severity rate of 3]

Likelihood Could happen sometime [Likelihood rate of 4]

Risk: from the risk

matrix

12 (Very High Risk)

Action Required Use a plan and systematic approach to risk control. Temporary

solution to control risk if necessary.

5.0 RESULT AND DISCUSSION

The document review method has revealed only few hazards. This is because the company did

not keep proper records of past incidents. Information gathered from the workers and

management was unreliable, the reason being that the memories of the workers involved were

vague. However, there were 2 clear cases of falling from ladders from 2 separate occasions

which was confirmed to be work related. These cases confirmed the need to do a JHA. There

were also 2 separate cases of malaria infection, although these cases which happen in different

times cannot be conclusively linked to the work environment.

The workplace inspection revealed plenty of hazards with regards to the environment of the

workplace, the condition of the tools used and the behavior and work style of the workers.

However most hazards identified like wet floor, stagnant water, uncovered holes on the ground

and unguarded staircases were not under our immediate control. These hazards were brought to

the attention of the site safety officer and the safety committee which have highlighted the issues

and hazards to the main site management team.

Therefore, most of the discussion on hazards identification in this report will be on the job

hazard analysis. This is a process by which our direct intervention will have the most impact on

the safety and health of the field operation worker of the company.

5.1 LIST OF HAZARDS:

The selected process was installing air conditioning duct at ceiling slab. It was a common

process which forms the bulk of the work onsite for the installers.

The following is the work process and the list of potential hazards:-

NO WORK

ACTIVITY

HAZARD HAZARD

TYPE

POTENTIAL

EFFECTS

1 Installing support

bracket on the

ceiling

Mineral dust from

drilling holes on ceiling

Health Respiratory complications

Awkward working

position

Health Muscular skeletal

disorder

Working at height Safety Fatal impact injuries

2 Assemble duct

sections on the floor

Sharp metal edges Safety Cuts

Work while swatting on

the floor


disorder

Noise from hammering

metals sheets

Health Mental irritability and lost

of concentration

3 Wrapping main duct

with insulation on

the floor

Loose fibers from

insulation

Health Respiratory complications

Organic solvents from

glue use

Health Brain damage

4 Hoisting and

positioning duct

sections onto

bracket in ceiling

Falling duct or tools Safety Crushing worker below

Manual handling of

heavy load

Health Muscular and physical

injury


5 Connecting adjacent

ducts in the ceiling

together

Awkward working

position


disorder

Falling duct or tools Safety Crushing worker below


6 Wrapping main duct

with insulation on

the floor


Falling tools Safety Non fatal impact injuries

to worker below

5.2 PRIORITISING HAZARDS/ RISK ASSESSMENT

5.2.1. RISK ASSESSMENT FOR SAFETY HAZARDS

JOB: INSTALLING AIR CONDITIONING DUCT AT CEILING SLAB

With S= Severity, L=Likelihood and R=Risk

From the risk assessment above, the safety hazards with the highest risk is “doing heavy work

while at heights” during hoisting and positioning of duct sections onto bracket in ceiling, with

worst possible effects of fatal impact injuries to the worker which is rated Very High Risk.

NO WORK

ACTIVITY

HAZARD POTENTIAL

EFFECTS

S L R RISK

DESCRIPTION

1 Installing

support bracket

on the ceiling

Working at

height

Fatal impact

injuries

4 2 8 MEDIUM RISK

2 Assemble duct

sections on the

floor

Sharp metal

edges

Cuts 1 4 4 LOW RISK

4 Hoisting and

positioning

duct sections

onto bracket in

ceiling

Falling duct or

tools

Crushing worker

below

3 3 9 MEDIUM RISK

5 Doing heavy

work while at

height

Fatal impact

injuries

4 4 16 VERY HIGH

RISK

6 Connecting

adjacent ducts in

the ceiling

together

Falling duct or

tools

Crushing worker

below

3 2 8 MEDIUM RISK

Working at

height

Fatal impact

injuries

4 2 8 MEDIUM RISK

7 Wrapping main

duct with

insulation on the

floor

Working at

height

Fatal impact

injuries

4 2 8 MEDIUM RISK

Falling tools Non fatal impact

injuries to

worker below

3 3 9 MEDIUM RISK

5.2.2 RISK ASSESSMENT FOR HEALTH HAZARDS

JOB: INSTALLING AIR CONDITIONING DUCT AT CEILING SLAB

With S= Severity, L=Likelihood and R=Risk

From the risk assessment above, the health hazard with the highest risk is “Organic solvents

from glue use” during wrapping main duct with insulation on the floor, with worst possible

effects of brain damage to the worker which is rated Very High Risk.

NO WORK

ACTIVITY

HAZARD POTENTIAL

EFFECTS

S L R RISK

DESCRIPTION

1 Installing

support bracket

on the ceiling

Mineral dust

from drilling

holes on

ceiling

Respiratory

complications

3 3 9 MEDIUM RISK

Awkward

working

position

Muscular

skeletal disorder

2 4 8 MEDIUM RISK

2 Assemble duct

sections on the

floor

Work while

swatting on the

floor

Muscular

skeletal disorder

2 3 6 MEDIUM RISK

Noise from

hammering

metals sheets

Mental

irritability and

lost of

concentration

2 4 8 MEDIUM RISK

3 Wrapping

main duct with

insulation on

the floor

Loose fibers

from insulation

Respiratory

complications

2 2 4 LOW RISK

Organic

solvents from

glue use

Brain Damage 5 3 15 VERY HIGH

RISK

4 Hoisting and

positioning duct

sections onto

bracket in

ceiling

Carrying and

holding still

duct

Muscular and

physical injury

3 4 12 MEDIUM RISK

5 Connecting

adjacent ducts in

the ceiling

together

Awkward

working

position

Muscular

skeletal disorder

2 2 4 LOW RISK

5.2.3 RATIONIZATION OF CRITICAL HAZARD

The critical hazards are chosen after careful consideration of the work activity and the work

environment and the feedback from the workers. Some activities had similar severity but the

effects on the worker are not immediately noticeable. The most critical hazards selected here are

related to symptoms already present in the workers.

5.2.3.1 SAFETY CRITICAL HAZARD JUSTIFICATION

WORK

ACTIVITY

HAZARD JUSTIFICATION

Hoisting and

positioning duct

sections onto

bracket in

ceiling

Doing heavy

work while at

height

SEVERITY:

Estimated one dead

Fatal because falling from height will expose the

body to impact on hard or sharp objects. In a hall,

the ceiling can be 10 meters high. The workers are

often working on a plywood platform supported by

scaffolding.

LIKELIHOOD:

Maybe will happen, would not be unusual

Workers feedback indicated that during this

process, utmost attention is paid to positioning and

getting the work material in position. Because of

this, the workers do not pay attention to their own

safety. Everyone focusing on doing work, including

the supervisor whom is responsible for the safety of

the operation. In the past, 2 incidents of workers

failing down from ladders was while engaging in

this activity.

5.2.3.2 HEALTH CRITICAL HAZARD JUSTIFICATION

5.3 IMPACT OF CRITICAL HAZARDS

Should there be fatality amongst the workers; the company will be impacted by:

1) Lost of time to do investigation, staff replacement, explaining to DOSH, reporting time,

supervisor time, make claims for the worker from SOSCO.

2) Lost of profits due to compensation to the family of the deceased, lost of productivity

among workers because of low morale

3) Lost of reputation and its subsequent disadvantages

4) Lost of profits due to lower productivity and efficiency and momentum

WORK

ACTIVITY

HAZARD JUSTIFICATION

Wrapping main

duct with

insulation on the

floor

Organic

solvents from

glue use

SEVERITY:

Multiple Brain Damage

Multiple brain damage because glue used in the

wrapping of the insulation contains toluene & n

hexane. The worst effects of which through

accumulated exposure is brain damage. The

workers after gluing sometimes experience being

“high” with glue. The solvent in the glue is also a

highly flammable liquid.

LIKELIHOOD:

Maybe will happen in the future

There has not been a reported case of brain damage

amongst the workers. However, as the company is

still a young company, the effects might not be seen

until much further longer in the future.

6.0 RECOMMENDATIONS

6.1 RECOMMENDED CONTROL MEASURES

The hierarchy of control to recommend control measures for hazards. The hierarchy o f control

from the most effective to the least effective are:

a) Most Effective – Elimination

b) Moderately Effective – Substitution

c) Moderately Effective – Engineering Controls

d) Moderately Effective – Administrative Controls

e) Least Effective – Personal Protective Equipment (PPE)

They are not mutually exclusive. The presence of a more effective control does not mean that

the less effective control measures were disregarded. They elimination and substitution control

measure is often not feasible as they often require a change of work process or materials which

involves a lot of factors, i.e. economics, practicality. On the other hand, PPE is often mistaken as

the simplest way to control a hazard. PPE should only be the control measure of last resort. It is

used only when even with the implementation of other control measures, hazards is still exist

6.1.1 RECOMMENDED CONTROL MEASURES FOR SAFETY HAZARD

The control measures below were prepared using hierarchy of controls.

Work Activity: Hoisting and positioning duct sections onto bracket in ceiling

Hazard: Doing heavy work while at height

HIERARCHY

OF CONTROL

RISK CONTROL

Elimination

Not feasible as the ducts to be installed in high ceiling are

determined by engineer requirement.

Substitution

Not feasible as the ducts to be installed in high ceiling are

determined by engineer requirement.

Engineering

Control

To provide elevated working platform with chain block hoist

Administration

Control

To require a supervisor to halt work if safety of worker

compromised.

To train and remind installers the proper method of working at

height. To strictly enforce the safe work procedures.

PPE

Compulsory use of hard hat and non slip safety boots. Protection

from fall devices like safety harness or safety belt.

6.1.2 RECOMMENDED CONTROL MEASURES FOR HEALTH HAZARD

The control measures below were prepared using hierarchy of controls.

Work Activity: Wrapping main duct with insulation on the floor

Hazard: Organic solvents from glue use

HIERARCHY

OF CONTROL

RISK CONTROL

Elimination

Not feasible as gluing insulation is compulsory part of the duct

installation process.

Substitution

Not feasible

A preinsulated duct is available in the market. However, the

insulation is not fire proof and therefore cannot be used in multiple

story buildings

Engineering

Control

Ventilate area of work to dilute organic solvents

Workers trained to recognize the effects of organic solvents and to

remove themselves from the work place if necessary.

Administration

Control

Require workers to do gluing in open area. Strictly prohibit

smoking, eating or drinking in the work place. Avoid any kind of

spark in the area. Ensure all lids of containers are closed when not

in use

PPE

Provide safety goggles, apron and solvent resistant hand glove for

workers.

6.2 REVIEW PLAN

A review plan is important to ensure the recommendations are implemented and to monitor the

effectiveness of the control measures.

Therefore, there will be a re evaluation of the critical hazard by inspection. Periodic inspection

at regular intervals of 2 months will be done. The inspector will also have to ask for feedback

from the workers to ensure that they also do their part in ensuring their own and of their

colleagues’ safety.

6.2.1 REVIEW PLAN FOR SAFETY HAZARD

Work Activity: Hoisting and positioning duct sections onto bracket in ceiling

Hazard: Doing heavy work while at height

Review Period: 2 months

Item Description Action By

1 Work place inspection to identify the scaffolding

provided are indeed safe for use, hoisting done

properly

Supervisor

2 To review effectiveness of training by testing worker

understand of their roles, work and their awareness of

the critical hazards and its effects

Safety Supervisor/

Officer

3 To check the condition of equipment used for work

such as chain block hoist, scaffolding

Supervisor

4 To check the condition and use of PPE Supervisor

5 To record all findings and to report to the

management

Safety Supervisor/

Officer

6.2.1 REVIEW PLAN FOR HEALTH HAZARD

Work Activity: Wrapping main duct with insulation on the floor

Hazard: Organic solvents from glue use

Review Period: 2 months

Item Description Action By

1 Work place inspection to identify ventilation

provided is sufficient or not

Supervisor

2 To review effectiveness of training by testing worker

understand of their roles, work and their awareness of

the critical hazards and its effects

Safety Supervisor/

Officer

3 To check the condition and use of PPE Supervisor

4 To record all findings and to report to the

management

Safety Supervisor/

Officer

6.3 CONTROL MEASURES BENEFIT

Implementing the control measures will give the employer the following benefits:

1) Better worker morale and support

2) Promote work efficiency and productivity

3) Compliance with legal requirements

4) Protect against lost time injuries and uninsurable cost

5) Protect its reputation

7.0 REFERENCES

Book references

i Jabatan Keselamatan dan Kesihatan Pekerjaan, Garis Panduan bagi

Mengenalpastian Hazard, Penaksiran Risiko dan Kawalan Risiko

[HIRARC] 2008

ii NIOSH Malaysia

Training Manual for Safety and Health Officer Certificate Programme

iii International Law Book Services

Factory and Machinery Act 1967, Regulations & Rules (As at 25th January

2010)

iv International Law Book Services

Occupational Safety & Health Act 1994, Regulations & Rules (As at 25th

January 2010)

v SOCSO

Social Security Organisation Annual Report 2009

vii ILO Publications

Safety in Use of Synthetic Vitreous Fibre Insulation Wools 2001

viii National Institute for Occupational Safety and Health, USA

NIOSH POCKET GUIDE TO CHEMICAL HAZARDS

ix Hughes & Ferrett by Butterworth-Heinemann

Introduction to Health and Safety in Construction2007

Website references

i Department of Occupational Safety and Health, Malaysia

www.dosh.gov.my

ii Canada's National Centre for Occupational Health and Safety

www.ccohs.ca

iii HSE, UK

www.hse.gov.uk

iv Encyclopedia of Occupational Health & Safety

www.ilo.org

v Wikipedia

en.wikipedia.org/wiki/occupational_safety_and_health

8.0 APPENDICES

CONTENTS

8.1 Related MSDS

8.2 Photographs of work

8.3 Statistics

niosh wpa- glomax

Documents