An Evaluation of a Workplace Hazard: Carbon Monoxide

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An Evaluation of a Workplace Hazard: Carbon Monoxide . University of Central Florida, Introduction to Industrial Hygiene EIN 6264 April 1998 Submitted by, Tim Wallace, R.S Identification of Workplace Hazard.
An Evaluation of a Workplace Hazard: Carbon Monoxide

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An evaluation of a workplace hazard carbon monoxide l.jpgSlide 1

An Evaluation of a Workplace Hazard: Carbon Monoxide

University of Central Florida,

Introduction to Industrial Hygiene

EIN 6264

April 1998

Submitted by,

Tim Wallace, R.S

Identification of workplace hazard l.jpgSlide 2

Identification of Workplace Hazard

  • Carbon Monoxide (CO) = a chemical compound consisting of one carbon and one oxygen.

  • CO is a colorless and odorless gas at room temperature. Therefore, it has no WARNING properties!!!!

  • The most likely route of exposure is through inhalation.

Extent of hazard osha says l.jpgSlide 3

Extent of Hazard-OSHA Says:

  • “Some 2,000 persons a year are killed out right by CO gas exposure”

  • “At least 10,000 more workers suffer from exposure to debilitating levels of CO”

  • “One of the most dangerous industrial hazards”

  • “One of the most widespread”

Nature of hazard l.jpgSlide 4

Primarily known as an asphixiant or chemical anoxiant. This means that the CO causes absence or abnormally low amounts of oxygen in the body

CO simply disrupts the oxygen transport to all tissues in the body.

CO combines with hemoglobin in blood to form carboxyhemoglobin (COHb)

Nature of Hazard

Nature of hazard ii l.jpgSlide 5

Nature of Hazard II

  • CO has an affinity for the oxygen binding site in the blood; 200 times more so than oxygen

  • Other Potential Hazards (Atypical): highly flammable, may form explosive mixtures when mixed in air, may react to finely dispersed metal powders to form toxic and flammable carbonyls, may react vigorously w/ oxygen, acetylene, chlorine, fluorine, nitrous oxide.

  • Other Physical Properties: BP -191ºC, MP -205°C, Explosive Limits (volume % in air) 12.5-74.2

Health effects target organs or systems l.jpgSlide 6


Cardiovascular System


Central Nervous System

Tissues with the highest oxygen need are first affected:



exercising muscles

Health Effects (Target Organs or Systems)

Symptoms of exposure l.jpgSlide 7

Symptoms of Exposure

Particularly susceptible populations l.jpgSlide 8

Particularly Susceptible Populations

  • Elderly

  • Pregnant Women and Young Children

  • Smokers

  • Persons with existing illnesses: WHY???

    a. cardiovascular disease (heart disease, coronary artery disease)

    b. pulmonary disease (asthma, emphysema, chronic bronchitis)

    c. blood disorders (sickle cell anemia, lassemia, others)

Sources of co l.jpgSlide 9

Sources of CO

  • Incomplete combustion of anything containing carbon (fossil fuels, wood, tobacco) - Especially high in exhaust from internal combustion engines.

  • CO is a metabolic product of methylene chloride (common ingredient in paints and solvents)

  • may be be produced within the body by catabolism (breakdown) of hemoglobin

Typical occupations that may experience co hazard l.jpgSlide 10

fire fighters

garage mechanics

aircraft refuelers

truck Drivers

Kiln and furnace operators

forklift operators

lawn care workers

janitorial staff

disaster relief workers


parking garage attendants

toll collectors

agricultural workers

Typical Occupations that May Experience CO Hazard

Standard methods of measurement assessment l.jpgSlide 11

Standard Methods of Measurement/Assessment

  • Direct reading CO Detector (electro-chemical voltimetric sensor) - dataloger and calibration to known gas concentration required

  • sampling with calibrated vacuum pump through adsorption tube - laboratory analysis

  • detector tubes certified by NIOSH

  • all samples or measurements should be in the worker’s “breathing zone”

Other methods epa outside air methods l.jpgSlide 12

Other Methods (EPA Outside Air Methods)

  • Gas Filter Correlation (GFC) - relies on infrared absorbency properties of CO at 4.7, High accuracy, greater sensitivity, more complex equipment, stationary measurement

  • Nondispersive Infrared (NDIR) - CO has a characteristic spectrum that allows it to be measured with reference to IR energy absorbed. Sensitive to drift, allows continuous datalogging, requires warm-up time, operable by non-technical personnel

Applicable ih standards l.jpgSlide 13


NIOSH REL=35 ppm TWA; 200 ppm ceiling

NIOSH IDLH=1,200 ppm


EPA NAAQS (Primary Standard) for outside air=9 ppm (TWA 8 hrs), =35 ppm (TWA 1 hr). This was established to protect public health (susceptible populations)

Applicable IH Standards

Still more tlv s international flavor l.jpgSlide 14

DFG MAK (Germany) TWA = 30 ppm PEAK = 60 ppm (30 min)

Japan (JSOH) TWA = 50 ppm

HSE OES (United Kingdom) TWA = 50 ppm STEL = 300 ppm

Reference: “TLVs and Other Occupational Exposure Values”

Still More TLV’s (International Flavor)

Other guidelines l.jpgSlide 15

NRC (1987) EEGLs: 10 min = 1,500 ppm 30 min = 800 ppm 60 min = 400 ppm 24 hrs = 50 ppm

NRC = National Research Council

EEGL is Emergency Exposure Guidance Levels

Canadian IAQ Residential Exposure Guidelines: <11 ppm for 8 hrs, <25 ppm for 1hr (ASTER)

WHO Concentration of Concern is >30 ppm

Other Guidelines

Co study occupation lawn care worker l.jpgSlide 16

My project was a simulation of lawn care worker.

8 hour work day (~ 6 hrs of mowing)

work equipment varied

some CO exposure expected

Mowed two properties.

One property was approximately 1 acre and was mowed with push mower

2nd property was about 2.5 acres and was mowed by riding mower

CO Study, Occupation: Lawn Care Worker

Specific job duties of worker during study period l.jpgSlide 17

Specific Job Duties of Worker During Study Period

  • To operate gasoline powered mowers to mow two properties

  • Edging not included

  • To obtain gas for mower if empty

Subject of study l.jpgSlide 18

Question: Will CO Exposure exceed any standards or guidelines during a simulated average 8-hour work shift for an Lawn Care Worker?

There seems to be few published reports on this type of a study. Some reports focus on small gasoline engines used inside buildings where the CO is easily concentrated.

Subject of Study:

Equipment in use l.jpgSlide 19

Equipment in Use

  • Push mower

  • riding lawn tractor

  • automobile (to move between sites)

Ih equipment used for hazard assessment l.jpgSlide 20

IH Equipment Used for Hazard Assessment

  • Metrosonics PIM 1100 Industrial Hygiene Personal Monitor - Courtesy of Metrosonics, Inc.CO Electrochemical Oxidation Sensorwith a Heat Stress Monitor (core temperature and heart beats per minute)with Noise monitor (slow, A-weight)

Findings l.jpgSlide 21


  • Minimum 0 ppm

  • Average 5 ppm

  • Maximum 150 ppm

  • 15 min STEL 13 ppm

  • TWA 5 ppm

Comparison to exposure guidelines and standards l.jpgSlide 22

Comparison to Exposure Guidelines and Standards

  • The OSHA PEL TWA was not exceeded.

  • The NIOSH REL TWA was not exceeded.

  • The NIOSH Ceiling was not exceeded.

  • The ACGIH TLV was not exceeded.

  • None of the other suggested guidelines were exceeded.

Comments on data l.jpgSlide 23

The momentary CO level measured during the start-up of the riding mower was elevated, however the duration of the exposure was short.

Graph of Data (available as handout)

Breaks and Lunch are distinct on data graph

Comments on Data

Possible co hazard control measures if needed l.jpgSlide 24

Possible CO Hazard Control Measures (if needed)

  • Eliminate - ex. Substitute gas mower with electric or manual mower.

  • Control Source - ex. Adjust equipment to control emissions (catalytic converters) or improve efficiency of combustion process

  • Apply appropriate ventilation or exhaust mechanism (only inside enclosures), ensure proper operation of exhausts

More co hazard control measures l.jpgSlide 25

More CO Hazard Control Measures

  • Provide appropriate personal protective equipment (PPE) to workers, when sources can not be controlled or eliminated and levels are suspected as hazardous. SCBA (NIOSH specified) is often specified. Definitely applies to fire/rescue personnel.

Summary of key points l.jpgSlide 26

Carbon Monoxide exposure is a serious health and safety hazard.

CO is especially a hazard in enclosed spaces

CO did not seem to be a serious hazard during normal mowing operations.

If CO levels were high and exceeded applicable TLVs, Control measures could be effectively instituted.

Summary of Key Points

Conclusion no co standards or guidelines exceeded l.jpgSlide 27

Conclusion: No CO Standards or Guidelines Exceeded

  • If this simulation was representative of a normal workday of a lawn care worker, then it appears that CO does not pose a serious threat to normal healthy adults.

  • It is conceivable that that these low level exposures may cause measurable effects in susceptible individuals. More data is needed.

Note other potential hazards associated w featured occupation l.jpgSlide 28

Heat Stress


Injuries (overturned tractors, cuts, eye injuries, thrown debris)

fire (burns)

UV radiation exposure

exposure to bioaerosols (mold spores, pollen) - a problem for asthmatics and allergy sufferers

Note: Other Potential Hazards Associated w/ Featured Occupation

Note co can be a hazard in nonoccupational settings l.jpgSlide 29

Note: CO can be a Hazard in Nonoccupational Settings

  • Schools

  • Homes

  • Commuting

  • Hospitals

  • Nursing Homes

Electronic resources l.jpgSlide 30

Electronic Resources

  • Internet:






Acknowledgements l.jpgSlide 31


  • Thanks goes to:

    • Jennifer, Ed Williams and Mary Gestaldi for use of their property (land and work equipment)

    • James Slattery from Metrosonics, Inc. for use of IH equipment

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