December 18, 2000

 HETA 2001-0026

Rice C. Leach, M.D., Commissioner

Cabinet for Health Services

Commonwealth of Kentucky

Department for Public Health

275 East Main Street

Frankfort, Kentucky 40621-0001

Dear Dr. Leach:

On October 13, 2000, the National Institute for Occupational Safety and Health (NIOSH)

received a request from the Cabinet for Health Services in the Commonwealth of Kentucky to

evaluate carbon monoxide (CO) concentrations associated with the operation of houseboats on

Lake Cumberland. On October 23 - 25, 2000, NIOSH investigators conducted a site visit at

Lake Cumberland to investigate CO concentrations on houseboats located at the State dock,

Jamestown dock, and Alligator II dock. This letter describes our evaluation methods, findings,

and conclusions.

Background

Previous investigations were performed by NIOSH industrial hygienists and representatives from

several agencies in September, 2000 and October, 2000 in response to CO related poisonings and

deaths on houseboats at Lake Powell, AZ. These investigations characterized the circumstances

of boat related CO poisonings through review of emergency medical service (EMS) transport

records, and measured hazardous CO concentrations on houseboats.1, 2 Incident reports provided

by the National Park Service revealed 9 known boat-related CO poisoning deaths on Lake

Powell since 1994. Some of these incidents involved multiple poisonings in addition to the

deaths reported (total of 25 people poisoned in the 8 incidents involving fatalities). Information

regarding the fatalities was provided in a previous report.1

Some of the severely hazardous situations identified during the September and October, 2000

evaluations at Lake Powell, AZ included:

! The open space under the swim platform could be lethal under certain circumstances

(i.e., generator/motor exhaust discharging into this area) on some houseboats. 

! Some CO concentrations above and around the swim platform were at or above the

immediately dangerous to life and health (IDLH) level [greater than 1,200 parts of

CO per million parts of air (ppm)]. 
Page 2 - Dr. Rice Leach, Commissioner

! Measurements of personal CO exposure during boat maintenance activities indicated

that employees may be exposed to hazardous concentrations of CO. 

Please refer to Attachments 1 and 2 for discussions of health effects of CO exposure and relevant

evaluation criteria. 

 

Methods and Materials

During our investigation at Lake Cumberland, CO was measured in the space below the swim

deck (on houseboats where the generator exhaust discharged into this area) and the area on the

back of houseboats with only the generator operating, and with the generator and boat engines

operating simultaneously. 

CO concentrations were measured on the back of the houseboats using ToxiUltra Atmospheric

Monitors (Biometrics, Inc., Middletown, CT) with CO sensors. All ToxiUltra CO monitors were

calibrated before and after each use according to the manufacturer’s recommendations. These

monitors are direct-reading instruments with data logging capabilities. The instruments were

operated in the passive diffusion mode, with a 15 - 30 second sampling interval. The

instruments have a nominal range from 0 ppm to 500 ppm with the highest instantaneous reading

of 1000 ppm. Figure 1 illustrates a typical houseboat and where ToxiUltra CO monitors were

placed. Some of the locations varied on different houseboats depending on the swim deck and

swim platform designs.

CO measurements were also made with detector tubes [Drager CO, CH 29901– range 0.3%

(3,000 ppm) to 7% (70,000 ppm)] in the areas below and around the swim deck. The detector

tubes are used by drawing air through the tube with a bellows–type pump. The resulting length

of the stain in the tube (produced by a chemical reaction with the sorbent) is proportional to the

concentration of the air contaminant.

“Grab” samples were collected using Mine Safety and Health Administration (MSHA) 50–mL

glass evacuated containers. These samples were collected by snapping open the top of the

evacuated glass container and allowing the air to enter. The containers were sealed with

wax–impregnated MSHA caps. The samples were then sent by overnight delivery to the MSHA

laboratory in Pittsburgh, Pennsylvania where they were analyzed for CO using a HP6890 gas

chromatograph equipped with dual columns (molecular sieve and porapak) and thermal

conductivity detectors. 

Results

Navigator Houseboat 

During the early afternoon on October 23, 2000, CO samples were collected on a 2000 model

Navigator houseboat with the specifications listed below. The diesel generator ran 
Page 3 - Dr. Rice Leach, Commissioner

approximately 38 minutes and the diesel motors ran approximately 20 minutes during this

evaluation.

Engines: Two 4 cylinder diesel Volvo Penta 150 HP engines

Generator: 20 Kw Onan, 4 cylinder diesel generator

Exhaust Configuration: Generator exhaust discharged out the back corner of

swim platform (into the open area around the corner of swim platform). 

Air speed above deck: air speed readings ranged between 108 - 268 feet per

minute

Air speed below deck: air speed readings ranged between 2 - 17 feet per minute

Area around exhaust and off back of houseboat

Figure 2 shows a portion of the back deck of the Navigator houseboat, and also illustrates the

generator exhaust discharging out the back corner of the swim platform. An evacuated glass

container measurement in this area indicated a CO concentration of 13 ppm. A similar

measurement collected in an exhaust cloud off the back of the swim platform, at the water when

both the generator and motors were in operation, indicated a CO concentration of 27 ppm. A

third evacuated container sample collected on the swim platform with only the generator in

operation did not detect CO. 

Area Above Swim Deck on Back of Boat 

The prevailing air movement was toward the left back corner (when on back of boat and facing

the water) and flowing across the back deck. Smoke tube tests indicated that eddy currents were

being formed off the back of the swim platform. Table 1 lists the CO monitor results obtained

on the back of the Navigator houseboat, with the generator and motors operating. 

Table 1. Sample locations and CO results on the diesel powered Navigator houseboat.

Location CO average (ppm) CO peak (ppm)

On the back of the left slide (the slide on the left of

swim deck when on the boat and facing the water)

at breathing zone height

1.5 29

On the back of the right slide (the slide on the right

of swim deck when on the boat and facing the

water) at breathing zone height

1 21

Left side of swim platform (at floor level) 11 218*

Right side of the swim platform (at floor level) 8 128*

On the stairs between the two slides on the back

deck

1 24
Page 4 - Dr. Rice Leach, Commissioner

Location CO average (ppm) CO peak (ppm)

Near the sliding glass door on the back deck 5 161

On the top deck of boat 0.5 18

 Inside the boat 0.4 7

* CO monitors on the right and left sides of the swim platform were placed in exhaust cloud (see

Figure 2) off the back of the swim platform resulting in the reported CO peak concentrations.

Jamestown Boat Works Houseboat 

During the afternoon on October 23, 2000, CO samples were collected on a 1995 model

Jamestown Boat Works houseboat with the specifications listed below. The diesel generator ran

approximately 43 minutes and the motors ran approximately 23 minutes during this evaluation.

Engines: Two gasoline outboard Evinrude 88 HP engines

Generator: 10.5 Kw Lugger, 3 cylinder diesel generator

Exhaust Configuration: Generator exhaust out the back corner of swim

platform. See Figure 3 for exhaust discharge.

Air speed above deck: air speed readings ranged between 144 - 247 feet per

minute

Air speed below deck: air speed readings ranged between 13 - 55 feet per

minute

Area around exhaust off back of houseboat

An evacuated glass container used in the area around the exhaust of the diesel generator did not

detect the presence of CO. 

Area Above Swim Deck on Back of Boat 

The prevailing air movement was across the back right corner of the rear deck (when on back of

boat and facing the water) and flowing toward the left corner of the swim platform (where the

generator exhaust was located) at 144-247 fpm. Table 2 lists the CO monitor results.

Table 2. Sample locations and CO results on the Jamestown Boat Works houseboat.

Location CO average (ppm) CO peak (ppm)

Only Diesel Generator Running (ran for approximately 20 minutes without motors operating)

On the back of the slide at breathing zone height CO not detected

Right side of the swim platform (at floor level) 1 6
Page 5 - Dr. Rice Leach, Commissioner

Location CO average (ppm) CO peak (ppm)

Only Diesel Generator Running (ran for approximately 20 minutes without motors operating)

Left side of swim platform (at floor level) 1 10

On the ladder on swim platform 0.2 3

On stairs going up to top deck CO not detected

On the top deck of boat CO not detected

 Inside the boat CO not detected

Diesel Generator and Gasoline powered Outboard Motors Running (ran together for

approximately 23 minutes)

On the back of the slide at breathing zone height 11 116

Right side of the swim platform (at floor level) 71 455

Left side of swim platform (at floor level) 56 200

On the ladder on swim platform 19 181

On stairs going up to top deck 6 53

On the top deck of boat 3 63

 Inside the boat 9 60

Stardust Houseboat 

During the morning on October 24, 2000, CO samples were collected on a 2000 model Stardust

houseboat with the specifications listed below. This houseboat was equipped with a gasoline

generator and motors. The generator ran approximately 65 minutes and the motors ran

approximately 15 minutes during this evaluation.

Engines: Two 4 cylinder Mercury Mercruiser engines

Generator: 15.0 Kw Westerbeke, 4 cylinder gasoline generator

Exhaust Configuration: Generator exhaust ran under swim deck and platform

and exhausted out the back of the boat.

Air speed above deck: air speed readings ranged between 180 - 605 feet per

minute

Air speed below deck: air speed readings ranged between 5-50 feet per minute
Page 6 - Dr. Rice Leach, Commissioner

Area around exhaust off back of houseboat and beneath swim deck

Two evacuated glass container samples and two detector tube samples were collected

approximately 6 - 12 inches above the water (off the back of the swim platform in the vicinity of

the generator exhaust) while the generator was in operation. This is an area where individuals

could conceivably swim around, and enter and exit the water. The two evacuated container

samples indicated CO concentrations of 426 and 4,662 ppm. A detector tube sample collected in

this same area indicated a CO concentration of 0.3 % (3,000 ppm). Another detector tube

collected in this area had a CO color change on the tube below the tube minimum scale reading

of 3,000 ppm. 

The ToxiUltra CO monitors have a nominal range from 0 ppm to 500 ppm with the highest

instantaneous reading of 1000 ppm. Exposing the CO monitor to concentrations greater than

1,000 ppm for extended periods can damage the sensor. Therefore, the CO monitors were placed

in the area off the back of the swim platform for only short periods of time to give brief

indications of CO concentrations. The monitors placed in this area indicated CO concentrations

greater than 1,000 ppm and therefore, were removed from the environment. 

A CO monitor was placed in the access port to the area beneath the swim deck on the boat while

the generator and motors were in operation. This monitor indicated CO concentrations greater

than 1,000 ppm. An evacuated container sample collected in this area indicated a CO

concentration of 818 ppm. A detector tube sample collected in this area had a CO color change

on the tube below the tube minimum scale reading value of 3,000 ppm.

Area Above Swim Deck on Back of Boat 

The air movement ranged between 180 - 605 fpm. The prevailing air movement was from the

right side of the back deck (when on back of boat and facing the water) and flowing across the

back deck toward the left side of the boat. Table 3 list the CO monitor results.

Table 3. Sample locations and CO results on the Stardust houseboat.

Location CO average (ppm) CO peak (ppm)

Only Generator Running (ran for approximately 65 minutes without motors operating)

On the back of the slide at breathing zone height 16 139

On stairs going up to top deck 8 188

Left side of swim platform (at floor level)* 170 885

Right side of the swim platform (at floor level)* 100 1170

On the top deck of boat 2 72
Page 7 - Dr. Rice Leach, Commissioner

 Inside the boat 8 89

Generator and Motors Running (ran together for approximately 15 minutes)

On the back of the slide at breathing zone height 5 46

On stairs going up to top deck CO not detected in this area during this

15 minute period

Left side of swim platform (at floor level)* 26 255

Right side of the swim platform (at floor level)* 14 198

On the top deck of boat 0.1 1

 Inside the boat 0.1 1

* See Figure 4 and 5 for graphical displays of the data collected on the swim platform.

Jamestown Deluxe Houseboat 

During the mid-afternoon on October 24, 2000, area CO samples were collected on a 1988

model Jamestown Deluxe houseboat with the specifications listed below. This houseboat was

equipped with a gasoline generator and motor. CO concentration data were collected while the

generator ran for approximately 57 minutes and while the motor and generator ran together for

approximately 24 minutes during this evaluation.

Engine: 4 cylinder, 140 HP, Mercury Mercruiser engine

Generator: 12.0 Kw Westerbeke, 4 cylinder gasoline generator

Exhaust Configuration: Generator exhaust ran under back deck and exhausted

out the back of the boat.

Air speed above deck: air speed readings ranged between 11 - 53 feet per minute

Air speed below deck: air speed readings ranged between 8 - 32 feet per minute

Area around back of houseboat and beneath swim deck

The Jamestown Deluxe houseboat did not have a swim platform that extended down to the water

level like other boats evaluated (see Figure 6). The generator and motor exhaust discharged out

the back of the boat into the area under the back deck. Evacuated glass container samples and

detector tube samples were collected approximately 12 inches above the water level off the back

deck when the generator was in operation. CO samples were also collected near the bottom of

the stairs that lead down to the water off the back deck (see Figure 6) where individuals could

conceivably swim around, and enter and exit the water.

The two evacuated container samples indicated CO concentrations of 1,157 and 663 ppm while

the generator was running. Detector tubes collected in this area indicated CO color changes on

the tube below the tube minimum scale reading value of 3,000 ppm. CO monitors placed in this
Page 8 - Dr. Rice Leach, Commissioner

area indicated CO concentrations of greater than 1,000 ppm. 

A CO monitor was placed in the access port to the area beneath the swim deck while the

generator and motors were in operation. This monitor indicated CO concentrations greater than

1,000 ppm. An evacuated container and a detector tube sample were collected in this area and

indicated CO concentrations of 818 and 1000 ppm, respectively. Another evacuated container

sample collected off the back of the boat while the motor and generator were in operation

indicated a CO concentration of 265 ppm.

Area Above Swim Deck on Back of Boat 

Table 4 lists the CO monitor results obtained on the back of the Jamestown Deluxe houseboat.

Table 4. Sample locations and CO results on the Jamestown Deluxe houseboat.

Location CO average (ppm) CO peak (ppm)

Only Generator Running (ran for approximately 57 minutes without motors operating)

On the back of the slide at breathing zone height 68 210

On stairs going up to top deck 54 204

Left side of back deck (at floor level)* 326 1122

Right side of back deck (at floor level)* 274 961

On the top deck of boat 9 62

 Inside the boat 59 109

On back deck at the sliding glass door 72 259

Generator and Motors Running (ran together for approximately 24 minutes)

On the back of the slide at breathing zone height 48 188

On stairs going up to top deck 42 158

Left side of back deck (at floor level)* 300 1121

Right side of back deck (at floor level)* 288 862

On the top deck of boat 3 33

 Inside the boat 40 166

On back deck at the sliding glass door 56 277

* See Figure 7 and 8 for graphical displays of the data collected at floor level on the back deck.
Page 9 - Dr. Rice Leach, Commissioner

Stardust Presidential Houseboat 

During the afternoon on October 24, 2000, area CO samples were collected on a 1998 model

Stardust houseboat with the specifications listed below. This houseboat was equipped with a

gasoline generator and two gasoline motors. CO concentration data was collected while the

generator ran for approximately 71 minutes and while the motors and generator ran together for

approximately 28 minutes during this evaluation.

Engine: Twin 4 cylinder, Mercury Mercruiser engines

Generator: 15.0 Kw Westerbeke, 4 cylinder gasoline generator

Exhaust Configuration: Generator and motors exhausted under swim deck.

Air speed above deck: air speed readings were mainly between 3 - 40 feet per

minute. However, wind gust were measured up to 735 fpm

Air speed below deck: air speed readings ranged between 21 - 43 feet per

minute

Area under swim deck and around swim platform of houseboat

The generator and motor exhaust discharged out the back of the boat into the area under the

swim deck. Evacuated glass container samples and detector tube samples were collected

approximately 6-12 inches above the water level off the back of the swim platform. Evacuated

container and detector tube samples were also collected in the view port into the area below the

swim deck where the generator and motors exhaust (see Figure 9). Samples were collected when

the generator was in operation and when the generator and motors were in operation

simultaneously.

The evacuated container sample collected off the back of the swim platform (near water level)

while only the generator was in operation indicated CO concentration of 4,078 ppm. An

evacuated container sample, collected in the area off the back of the swim platform when the

motors and generator were in operation, indicated a CO concentration of 10,224 ppm. This

sample also indicated that the area where the sample was collected was oxygen deficient (17.2 %

O2). [During the analysis of this sample the evacuated container was damaged, which may have

resulted in some loss of the sample. Thus, the result could be higher.] A detector tube sample

also collected in the area off the back of the swim platform (near water level) indicated a CO

concentration of 3,000 ppm when the generator and motors were in operation. 

An evacuated container sample and a detector tube sample collected in the view port into the

area below the swim deck while only the generator was in operation indicated CO concentrations

of 7,985 ppm and 3,000 ppm, respectively. An evacuated container sample collected in this area

when both the generator and motors were in operation indicated a CO concentration of 10,194

ppm. The two evacuated container samples collected below the swim deck with only the

generator operating and with the generator and motors operating simultaneously also indicated

that the area was oxygen deficient (18.5 % O2 and 17.7 % O2, respectively).
Page 10 - Dr. Rice Leach, Commissioner

Area Above Swim Deck on Back of Boat 

Table 5 list the CO monitor results obtained on the back of the Stardust Presidential houseboat.

Table 5. Sample locations and CO results on the Stardust houseboat (1998 model).

Location CO average (ppm) CO peak (ppm)

Only Generator Running (ran for approximately 71 minutes without motors operating)

On the back of the slide at breathing zone height 13 213

On stairs going up to top deck 23 239

Left side of swim platform (at floor level)* 271 1121

Right side of swim platform (at floor level)* 280 1221

On the top deck of boat 5 68

 Inside the boat 6 128

Generator and Motors Running (ran together for approximately 28 minutes)

On the back of the slide at breathing zone height 41 364

On stairs going up to top deck 32 197

Left side of swim platform (at floor level)* 501 1120

Right side of swim platform (at floor level)* 542 1221

On the top deck of boat 12 78

 Inside the boat 31 323

* See Figure 10 and 11 for graphical displays of the data collected on the swim platform. The

upper limit of the CO monitors were exceeded at times and the graphs depict flat lines at the top

of these peaks. 

Lakeview Houseboat 

During the morning on October 25, 2000, area CO samples were collected on a 1999 model

Lakeview houseboat with the specifications listed below. This houseboat was equipped with a

gasoline generator and two gasoline motors. The houseboat was taken out on the lake and

anchored in a cove during the evaluation. CO concentration data was collected while the

generator ran for approximately 25 minutes and while the motors and generator ran together for

approximately 52 minutes. CO data was collected on the trip out to the cove, in the cove, and on

the trip back to the dock. 
Page 11 - Dr. Rice Leach, Commissioner

Engine: Twin 4.3 liter V6 Mercury Mercruiser engines

Generator: 12.5 Kw Westerbeke, 4 cylinder gasoline generator

Exhaust Configuration: Generator exhausts to the side of the boat cabin

Air speed above deck: air speed readings ranged between 270 - 319 feet per

minute

Air speed below deck: air speed readings ranged between 123 - 210 feet per

minute

Area around swim platform of houseboat

The motors on this houseboat exhausted under the back of the swim deck and the generator

exhausted out to the side of the boat. An evacuated glass container sample collected

approximately 6-12 inches above the water off the back of the swim platform (with the motors

and generator in operation after the boat had been stopped in a cove) indicated a CO

concentration of 643 ppm. A CO monitor was briefly placed approximately 6-12 inches above

the water level off the back of the houseboat with the generator and motors in operation and

indicated a CO concentration greater than 1000 ppm. 

The motors were shut off, and another evacuated container sample was collected off the back of

the swim deck approximately 6-12 inches above the water level. CO was not detected in this

sample. A CO monitor was briefly placed at the side of the boat in the vicinity where the

generator exhaust is discharged. This monitor indicated a CO concentration of 500 ppm while

only the generator was in operation. 

Area Above Swim Deck on Back of Boat 

Table 6 list the CO monitor results obtained on the back of the Lakeview houseboat.

Table 6. Sample locations and CO results on the Lakeview houseboat.

Location CO average (ppm) CO peak (ppm)

Only Generator Running (ran for approximately 25 minutes without motors operating)

On stairs going up to top deck 0.5 5

Left side of swim platform (at floor level)* 78 503

Right side of swim platform (at floor level)* 35 234

On the top deck of boat 0.06 1

 Inside the boat 4 46

Near sliding glass door on back deck 0.04 1
Page 12 - Dr. Rice Leach, Commissioner

Generator and Motors Running (ran together for approximately 52 minutes)

On stairs going up to top deck 6 115

Left side of swim platform (at floor level)* 208 968

Right side of swim platform (at floor level)* 121 787

On the top deck of boat 3 64

 Inside the boat 5 55

Near sliding glass door on back deck 5 90

* See Figure 12 and 13 for graphical displays of the data collected on the swim platform.

Discussion and Recommendations

The CO concentrations measured on and around the houseboats with diesel generators were

considerably less than CO concentrations on and around houseboats with gasoline powered

generators and motors. 

Diesel engines typically produce less CO than gasoline powered engines. The second houseboat

evaluated (Jamestown Boat Works Houseboat) had a diesel generator with two outboard gasoline

powered motors. When the generator was in operation, CO concentrations were low (0 - 10

ppm) around the generator exhaust and at the back of the boat. However, when the gasoline

motors were in operation, CO concentrations increased considerably on the back of the boat and

swim platform (CO concentrations measured up to 455 ppm on swim platform). The gasoline

motors are used to power the boat and should not be in operation when the boat is stationary. 

The diesel generators evaluated in this study connect to an exhaust discharging out the back

corner of the swim platform (see Figures 2 and 3). To date, a houseboat with the diesel

generator exhausting under the back swim deck has not been evaluated. This type of design

could conceivably allow a build-up of CO in the area beneath the back deck.

When gasoline generators are in operation, the area under the swim deck and around the back of

the swim platform (near water level) on houseboats that exhaust the combustion gases in the

space below the back deck, are extremely hazardous (CO concentrations well above IDLH levels

were measured in this area at Lake Powell). These hazardous conditions also exist when the

engines are in operation on the boats. During this survey, only one of the houseboats (Stardust

1998 model) exhausted the generator under the swim deck. The area under the swim deck and

around the back of the swim platform (approximately 6-12 inches above the water where

individuals could conceivably be swimming) indicated CO environments well above the NIOSH

IDLH value of 1,200 ppm3

 (CO concentrations were measured up to 10,000 ppm in these areas). 

High CO concentrations and IDLH environments were also identified in the area off the back of

the swim deck (where individuals could conceivably be swimming) on houseboats that discharge

the generator exhaust out to the rear of the swim platform or deck.
Page 13 - Dr. Rice Leach, Commissioner

The generator on the Lakeview houseboat exhausted to the side of the boat. Samples indicated

CO concentrations up to 500 ppm around the generator exhaust and at the swim platform (left

side at floor level). When the motors were operated, CO concentrations were higher (up to 1000

ppm off back of swim platform). This was also the case when the boat was in transit to and from

the cove (see Figures 12 and 13). However, it is conceivable that if someone is in the vicinity of

the exhaust under certain environmental conditions (i.e., stagnant air movement or slight air

movement that allows the CO to migrate into occupied areas on the boat) CO poisonings could

occur. Also, with this type of exhaust design (gasoline generator exhaust located on the side of

the boat) CO poisonings could potentially occur if the exhaust is blocked such as tying two

houseboats together and thus, allowing exhaust gases to drift into the boats.

This investigation reaffirms issues of concern regarding the potential for CO exposure on

houseboats. Individuals swimming or working in the area under the swim platform, or around

the area directly behind the swim platform (with the gasoline generator in operation on

houseboats that exhaust the combustion gases in the space below the back deck, or out the back

of the deck) could be exposed to extremely high CO concentrations resulting in CO poisoning or

death within a short period of time. The area on the back deck of houseboats is also a concern. 

When the generator or motors are in operation, the area around the back deck of houseboats can

be hazardous under certain conditions (i.e., lack of air movement).1

This evaluation was performed in October which is not in the prime operating season for

houseboats. Activities at the dock were slow, due to the low number of houseboat rentals. 

Therefore, personal sampling was not conducted. However, general recommendations are

provided to help control potential worker CO exposures. In addition, recommendations are

provided to reduce the potential for CO exposure around and under the swim platform on

houseboats. 

1) Public education efforts must immediately inform and warn all individuals (including boat

owners, renters, and dock workers) potentially exposed to these CO hazards. Public education

programs should continue until engineering control solutions that eliminate the problem are in

place. 

An effort is being made to inform manufacturers of houseboats about the environmental data that

has been collected, and the related design concerns. On September 1, 2000, the National Park

Service (NPS) sent each of these manufacturers a letter informing them of the numerous deaths

that may be attributed to CO poisoning from houseboat generator and/or engine exhaust. In

these letters, the Park Service specifically pointed out that most of the deaths occurred when the

victim was either on the back deck or in the water near or under the swim platform. In addition

to this effort, the initial NIOSH letter describing the first evaluation of CO on houseboats at Lake

Powell was also sent to 58 houseboat manufacturers.1

 This effort should be continued until all

manufacturers are aware of the problem and solutions are formulated to redesign and correct the

exhaust configuration. This should also include the redesigning of side-exhausting boats to help

eliminate CO problems when boats are tied together, or when someone is in the area where the
Page 14 - Dr. Rice Leach, Commissioner

exhaust gases are expelled from the boat.

2) Previous investigations have indicated that boat mechanics can be exposed to high

concentrations of CO.1,2 Therefore, the feasibility and effectiveness of engineering controls

should be investigated to help control CO exposures to boat maintenance mechanics. If repairs

are conducted outside and at the boat dock (where electric power is easily available), the use of a

high volume fan or other air-moving device may be effective in preventing worker short-term

high-level exposures to CO. Research into potential engineering controls needs to be

accomplished to make sure that the workers’ breathing zone is protected from CO and that any

exhaust from these controls is discharged into a well-ventilated area that is not occupied;

therefore, eliminating the possibility of individuals breathing the exhaust from the control

device. 

3) Training about the severity of CO hazards in boating should be developed for marina

personnel, EMS providers, and hospital emergency department staff so that symptoms

experienced by either employees or other boat operators might be more easily associated with

exposures. This training should include both environmental data, as well as information about

the number and circumstances of CO poisonings on the lake. 

4) The U.S. NPS has launched an awareness campaign to inform boaters on Lake Powell about

boat-related CO hazards. This alert included press releases, flyers distributed to boat and dockspace renters, and verbal information included in the boat check-out training provided for users

of concessionaire rental boats. In November, 2000, your cabinet issued a statewide news release

regarding the hazards of CO behind houseboats.4

 Your cabinet should also distribute CO hazard

flyers to boat and dock-space renters. Verbal information should be included in the boat checkout training provided for users of rental boats. Training about the specific boat-related CO

hazards provided to houseboat renters, should include specific information about the

circumstances and number of poisonings and deaths that have been documented in previous CO

evaluations.1

 The training should include anecdotal information about deaths and near misses,

and should specifically target warnings against entering air spaces under the boat (such as the

cavity below the swim platform), or immediately behind the swim platform that may contain a

lethal atmosphere.

5) When houseboats are in the water, the area under the swim deck meets NIOSH and OSHA

criteria for a permit-required confined space; therefore, permit-required confined space

requirements should be followed before any workers enter this area. See Attachment 3 for a

discussion regarding the basis for this recommendation.

Thank you for your cooperation with this investigation, and for providing important data related

to this serious issue. Please contact me at (513) 841-4387 if you have any questions regarding

this evaluation. Jane McCammon at (303) 236-6233 is an additional contact who can answer

any questions or concerns you may have regarding CO fatalities and poisoning incident reports

on houseboats. 
Page 15 - Dr. Rice Leach, Commissioner

Sincerely, 

Ronald M. Hall, M.S. 

Industrial Hygienist 

Industrial Hygiene Section 

Hazard Evaluations and Technical 

 Assistance Branch 

 Division of Surveillance, Hazard 

 Evaluations and Field Studies

cc: Joe Foley, Dock Operations Supervisor

Dwight C. Hadley, Russell County Health Department

Jennifer Fields, Kentucky Commission of Fish and Wildlife

Dick Powell, USNPS Safety Director

Gary Anderson, Aramark Wahweap

Lloyd Olson, USNPS

Norm Peterson, Arizona Department of Health

Courtney Casillas, Arizona Public Information Officer

Wayne Ball, Utah Department of Health

Ted Woolley, Utah Parks and Recreation

R.J. Doubt, US Coast Guard

ADM Joyce Johnson, USCG

Mike Kaas, USDOI, Office of Managing Risk and Public Safety
Page 16 - Dr. Rice Leach, Commissioner

References

1. McCammon JB, Radtke, T [2000]. Letter of September 28, 2000, from J. McCammon,

National Institute for Occupational Safety and Health, Centers for Disease Control and

Prevention, Public Health Service, U.S. Department of Health and Human Services, and T.

Radtke, US Department of Interior, to Joe Alston, Park Superintendant, Glen Canyon National

Recreation Area, Page, Arizona.

2. Hall, RH, McCammon, JB [2000]. Letter of November 21, 2000, from R. Hall and J.

McCammon, National Institute for Occupational Safety and Health, Centers for Disease Control

and Prevention, Public Health Service, U.S. Department of Health and Human Services, to Joe

Alston, Park Superintendant, Glen Canyon National Recreation Area, Page, Arizona. 

3. NIOSH [2000]. Immediately dangerous to life and health concentrations. DHHS (NIOSH)

Publication NO. 2000-130, Pocket Guide to Chemical Hazards and other Databases., July.

4. Cabinet of Health Services, Commonwealth of Kentucky [November, 2000]. Statewide News

Release. Officials warn of Carbon Monoxide Levels Behind Houseboats and Tractors. 

Frankfort Kentucky. 
Page 17 - Dr. Rice Leach, Commissioner

Con pl

CO monitback of slizone heigh

CO monitor placed on right of swim platform

CO monitor placed on Top Deck of boatCO monitor placed on stairs atbreathing zone height

Figure 1. Swim platform and back deck of houseboat with CO sample locations.
Page 18 - Dr. Rice Leach, Commissioner

Generator exhaust 

Back Deck discharge

Swim Platform

Exhaust cloudoff back of boat

Figure 2. Back View of Navigator boatand generator exhaust discharge.
Page 19 - Dr. Rice Leach, Commissioner

Generator exhaust 

discharge

Figure 3. Generator exhaust discharge on the Jamestown Boat Works Houseboat.
Page 20 - Dr. Rice Leach, Commissioner

Stardust Houseboat (left side swim platform)

0

200

400

600

800

1000

10:04:48 10:26:24 10:48:00 11:09:36

Time 

CO Concentration (ppm)

Generator

operating

Generator

and Motors

operating

Stardust Houseboat (right side of swim platform)

0

200

400

600

800

1000

1200

1400

10:04:48 10:19:12 10:33:36 10:48:00 11:02:24 11:16:48

Time

CO Concentration (ppm)

Generator operating Generator and

Motors operating

Figure 4. Graphical display of CO concentration data collected on the left side of swim 

 platform. CO levels may have dropped when generator/engines where running 

 because of wind shifts or an increase in wind speed.

Figure 5. Graphical display of CO concentration data collected on the right side of swim platform. 

CO levels may have dropped when generator/engines where running because of wind shifts or

an increase in wind speed.
Page 21 - Dr. Rice Leach, Commissioner

Figure 6. Back deck of Jamestown Deluxe Houseboat 
Page 22 - Dr. Rice Leach, Commissioner

Jamestown Deluxe Houseboat (left side of back deck 

at floor level)

0

200

400

600

800

1000

1200

11:16:48 11:45:36 12:14:24 12:43:12

Time

CO Concentration (ppm)

Generator Operating

Generator and Motor 

operating

Jamestown Deluxe Houseboat (right side of back 

deck at floor level)

0

200

400

600

800

1000

1200

11:28:19 11:42:43 11:57:07 12:11:31 12:25:55 12:40:19

Time

CO Concentration (ppm)

Generator operating

Generator and Motor

operating

Figure 7. Graphical display of CO concentration data collected on the left side of back deck.

Figure 8. Graphical display of CO concentration data collected on the right side of back deck.
Page 23 - Dr. Rice Leach, Commissioner

View port into 

space below swim deck

where generator and 

motors exhaust

Figure 9. View port into area beneath the swim deck of the Stardust Houseboat (1998 model).
Page 24 - Dr. Rice Leach, Commissioner

Stardust Houseboat 

(left side of swim platform at floor level)

0

200

400

600

800

1000

1200

1400

14:45:36 15:07:12 15:28:48 15:50:24

Time (military)

CO Concentration (ppm)

Generator operating Generator and Motors

operating

Upper Limit

of CO monitor

was exceeded

Stardust Houseboat 

(right side of swim platform at floor level)

0

200

400

600

800

1000

1200

1400

14:45:36 15:03:27 15:21:19 15:39:10 15:57:01

Time (military)

CO Concentration (ppm)

Generator operating

Generator and motors

operating

Upper Limit

of CO monitor

was exceeded

Figure 10. CO monitor results on the left side of swim platform (Stardust Houseboat 1998 model).

Figure 11. CO monitor

results on the right side of swim platform (Stardust Houseboat 1998 model).
Page 25 - Dr. Rice Leach, Commissioner

Lakeview Houseboat

 (left side of swim platform at floor level)

0

200

400

600

800

1000

1200

9:48:58 10:06:14 10:23:31 10:40:48 10:58:05 11:15:22

Time

CO Concentration (ppm)

Generator/Motors

operating

Generator 

operating

Generator/Motors

operating

Moving to

Cove Stationary in Cove

Moving to

 Dock

Lakeview Houseboat 

(right side of swim platform at floor level)

0

100

200

300

400

500

600

700

800

900

9:50:24 10:04:48 10:19:12 10:33:36 10:48:00 11:02:24

Time

CO Concentration (ppm)

Generator/Motors

operating

Generator/Motors

operating

Generator 

operating

Moving to

Cove Stationary in Cove

Moving to

 Dock

Figure 12. CO monitor results on the left side of swim platform (Lakeview Houseboat).

Figure 13. CO monitor results on the right side of swim platform (Lakeview Houseboat).
Page 26 - Dr. Rice Leach, Commissioner

Attachment 1

Health Effects of Exposure to Carbon Monoxide

Carbon monoxide (CO) is a colorless, odorless, tasteless gas produced by incomplete burning of

carbon-containing materials such as gasoline or propane fuel. The initial symptoms of

CO poisoning may include headache, dizziness, drowsiness, or nausea. Symptoms may advance

to vomiting, loss of consciousness, and collapse if prolonged or high exposures are encountered. 

If the exposure level is high, loss of consciousness may occur without other symptoms. Coma or

death may occur if high exposures continue.(1-6) The display of symptoms varies widely from

individual to individual, and may occur sooner in susceptible individuals such as young or aged

people, people with preexisting lung or heart disease, or those living at high altitudes. 

Exposure to CO limits the ability of the blood to carry oxygen to the tissues by binding with the

hemoglobin to form carboxyhemoglobin (COHb). Blood has an estimated 210-250 times greater

affinity for CO than oxygen, thus the presence of CO in the blood can interfere with oxygen

uptake and delivery to the body. Once absorbed into the bloodstream, the half-life of bloodborne

CO at sea level and standard pressure is approximately five hours. This means that an initial

COHb level of 10% could be expected to drop to 5% in five hours, and then 2.5% in another five

hours. If oxygen is administered to the exposed person, as happens in emergency treatment, the

COHb concentration drops more quickly. Once exposed, the body compensates for the reduced

bloodborne oxygen by increasing cardiac output, thereby increasing blood flow to specific

oxygen-demanding organs such as the brain and heart. This ability may be limited by

preexisting heart or lung diseases that inhibit increased cardiac output. 

Altitude effects the toxicity of CO. With 50 ppm CO in the air, the COHb level in the blood is

approximately 1% higher at an altitude of 4,000 feet than at sea level. This occurs because the

partial pressure of oxygen (the gas pressure causing the oxygen to pass into the blood) at higher

altitudes is less than the partial pressure of CO. Furthermore, the effects of CO poisoning at

higher altitudes are more pronounced. For example, at an altitude of 14,000 feet, a 3% COHb

level in the blood has the same effect as a 20% COHb at sea level.(7)

References

1. NIOSH [1972]. Criteria for a recommended standard: occupational exposure to carbon

monoxide. Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Health

Services and Mental Health Administration, National Institute for Occupational Safety and

Health, DHEW (NIOSH) Publication No. 73-11000. 

2. NIOSH [1977]. Occupational diseases: a guide to their recognition. Revised ed. Cincinnati,

OH: U.S. Department of Health, Education, and Welfare, Public Health Service, Centers for

Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH)

Publication No. 77-181.
Page 27 - Dr. Rice Leach, Commissioner

3. NIOSH [1979]. A guide to work-relatedness of disease. Revised ed. Cincinnati, OH: U.S.

Department of Health, Education, and Welfare, Public Health Service, Centers for Disease

Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No.

79-116.

4. Proctor NH, Hughes JP, Fischman ML [1988]. Chemical hazards of the workplace. 

Philadelphia, PA: J.B. Lippincott Company.

5. ACGIH [1996]. Documentation of threshold limit values and biological exposure indices. 

Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

6. NIOSH [1999]. Pocket guide to chemical hazards. Cincinnati, OH: U.S. Department of

Health and Human Services, Public Health Service, Centers for Disease Control, National

Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 99-115. 

7. American Gas Association [1988]. What you should know about carbon monoxide. 

American Gas Association 1985 Operating Section Proceedings. American Gas Association,

Arlington, Virginia. 
Page 28 - Dr. Rice Leach, Commissioner

Attachment 2

Evaluation Criteria

Although NIOSH typically focuses on occupational safety and health issues, the Institute is a

public health agency, and cannot ignore the overlapping exposure concerns in this type of

setting. Lake Cumberland employees should be in a state of health typical of any industrial

worker. Thus, occupational criteria for CO exposure are applicable to that group. The general

boating public, however, may range from infant to aged, be in various states of health and

susceptibility, and be functioning at a higher rate of metabolism because of increased physical

activity. The effects of CO are more pronounced in a shorter time if the person is physically

active, very young, very old, or has preexisting health conditions such as lung or heart disease. 

Persons at extremes of age and persons with underlying health conditions may have marked

symptoms and may suffer serious complications at lower levels of carboxyhemoglobin.(1) The

occupational exposure limits noted below should not be used for interpreting general population

exposures because they would not provide the same degree of protection they do for the healthy

worker population. 

Occupational Exposure Criteria. As a guide to the evaluation of the hazards posed by

workplace exposures, NIOSH field staff employ environmental evaluation criteria for the

assessment of a number of chemical and physical agents. These criteria are intended to

suggest levels of exposure to which most workers may be exposed up to 10 hours per

day, 40 hours per week for a working lifetime without experiencing adverse health

effects. It is, however, important to note that not all workers will be protected from

adverse health effects even though their exposures are maintained below these levels. A

small percentage may experience adverse health effects because of individual

susceptibility, or a pre-existing medical condition. In addition, some hazardous

substances may act in combination with other workplace exposures, the general

environment, or with medications or personal habits of the worker to produce health

effects even if the occupational exposures are controlled at the level set by the criterion. 

These combined effects are often not considered in the evaluation criteria. Finally,

evaluation criteria may change over the years as new information on the toxic effects of

an agent become available.

The primary sources of environmental evaluation criteria for the workplace are: (1)

NIOSH Recommended Exposure Limits (RELs),(2) (2) the American Conference of

Governmental Industrial Hygienists’ (ACGIH®) Threshold Limit Values (TLVs®), (3) (3)

the legal requirements of the U.S. Department of Labor, Occupational Safety and Health

Administration (OSHA) Permissible Exposure Limits (PELs),(4) and (4) the American

Society of Heating, Refrigerating, and Air-ConditioningEngineers (ASHRAE) Standard

for ventilation for acceptable indoor air quality.(5) Employers are encouraged to follow

the more protective criterion listed.
Page 29 - Dr. Rice Leach, Commissioner

A TWA exposure refers to the average airborne concentration of a substance during a

normal 8-to-10-hour workday. Some substances have recommended short-term exposure

limits (STEL) or ceiling values which are intended to supplement the TWA where there

are recognized toxic effects from higher exposures over the short-term.

The NIOSH REL for CO is 35 ppm for full shift TWA exposure, with a ceiling limit of

200 ppm which should never be exceeded.(6,7) The NIOSH REL of 35 ppm is designed to

protect workers from health effects associated with COHb levels in excess of 5%.1

NIOSH has established the immediately dangerous to life and health (IDLH) value for

CO as 1,200 ppm.(8) An IDLH value is defined as a concentration at which an immediate

or delayed threat to life exists or that would interfere with an individual's ability to escape

unaided from a space.

The ACGIH recommends an eight-hour TWA TLV of 25 ppm based upon limiting shifts

in COHb levels to less than 3.5%, thus minimizing adverse neurobehavioral changes such

as headache, dizziness, etc, and to maintain cardiovascular exercise capacity.(9)

The OSHA PEL for CO is 50 ppm for an 8-hour TWA exposure.(10)

Health Criteria Relevant to the General Public. 

The US EPA has promulgated a National Ambient Air Quality Standard (NAAQS) for

CO. This standard requires that ambient air contain no more than 9 ppm CO for an 8-

hour TWA, and 35 ppm for a one-hour average.(11) The NAAQs for CO was established

to protect “the most sensitive members of the general population” by maintaining

increases in carboxyhemoglobin to less than 2.1%. 

References

1. Kales SN [1993] Carbon monoxide intoxication. American Family Physician 48(6):1100-

1104.

2. NIOSH [1992]. Recommendations for occupational safety and health: compendium of policy

documents and statements. Cincinnati, OH: U.S. Department of Health and Human Services,

Public Health Service, Centers for Disease Control and Prevention, National Institute for

Occupational Safety and Health, DHHS (NIOSH) Publication No. 92-100. 

3. ACGIH [2000]. 2000 TLVs® and BEIs®: threshold limit values for chemical substances and

physical agents. Cincinnati, OH: American Conference of Governmental industrial Hygienists.

4. Code of Federal Regulations [1997]. 29 CFR 1910.1000. Washington, DC: U.S.

Government Printing Office, Federal Register.

5. Public Law 91 – 596 Occupational safety and Health Act of 1970, Sec. 5.(a)(1).
Page 30 - Dr. Rice Leach, Commissioner

6. CDC [1988]. NIOSH recommendations for occupational safety and health standards 1988. 

Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service, Centers

for Disease Control; National Institute for Occupational Safety and Health. MMWR 37

(supp. S-7).

7. Code of Federal Regulations [1989]. 29 CFR 1910.1000. Washington, DC: U.S.

Government Printing Office, Federal Register.

8. NIOSH [2000]. Immediately dangerous to life and health concentrations. DHHS (NIOSH)

Publication NO. 2000-130, Pocket Guide to Chemical Hazards and other Databases., July.

9. ACGIH [1992]. Threshold limit values and biological exposure indices for 1992-1993. 

Cincinnati, OH: American Conference of Governmental Industrial Hygienists.

10. 29 CFR 1910.1000 Table Z-1: Limits for air contaminants. Code of Federal Regulations,

Department of Labor, Chapter XVII - Occupational Safety and Health Administration. 

11. US Environmental Protection Agency [1991]. Air quality criteria for carbon monoxide. 

Publication No. EPA-600/8-90/045F. Washington, D.C.
Page 31 - Dr. Rice Leach, Commissioner

Attachment 3

Record reviews at Lake Powell indicated that three CO poisonings occurred within the span of

12 days in August, 1998, as a result of entering the airspace beneath the swim deck for engine

maintenance or clearing ropes from propellers. In the first instance, a 56-year-old man died

when he swam under the swim platform several times while the boat generator was operating. 

Ten days later, a 24-year-old employee was working under a houseboat changing the engine

propeller while the boat generator was operating. He was found unconscious in the water and

transported to a nearby medical clinic, where he was treated for carbon monoxide inhalation. 

Two days later, a 38-year-old man entered the airspace beneath the swim deck after deactivating

the boat engines. Approximately 3 hours later, his body was located in approximately 8 feet of

water.

One of these incidents involved an employee that worked at the marina at Lake Powell. OSHA

regulation 29 CFR 1910.146 defines a confined space as a space that meets three criteria: (1) is

large enough and configured so that an employee can bodily enter and perform any assigned

work; (2) is a space that has limited or restricted means for entry or exit (for example, tanks,

vessels, storage bins, vaults, and pits that have limited means of entry); and (3) a space that is not

designed for continuous employee occupancy. The standard then defines a permit–required

confined space as a space that meets one or more of the following criteria: (1) a space that

contains or has a potential to contain a hazardous atmosphere; (2) a space that contains a material

that has the potential for engulfing (surrounding and capturing of a person by a liquid or finely

divided solid substance that can be aspirated and cause death or that can exert enough pressure to

cause death by strangulation, constriction, or crushing) the person entering the space; (3) the

internal configuration of the space is designed in a way that the person entering the space could

be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward

and tapers to a smaller cross section; or (4) a space that contains any other recognized serious

safety or health hazard.1

 NIOSH defines a confined space as “an area which by design has

limited openings for entry and exit, unfavorable natural ventilation which could contain (or

produce) dangerous air contaminates, and which is not intended for continuous employee

occupancy. The NIOSH criteria for working in confined spaces further classifies confined

spaces based upon the atmospheric characteristics such as oxygen level, flammability, and

toxicity. As shown in Table 1, if any of the hazards present a situation which is immediately

dangerous to life or health (IDLH), the confined space is designated Class A. A Class B

confined space has the potential for causing injury and/or illness, but is not an IDLH atmosphere. 

A Class C confined space is one in which the hazard potential would not require any special

modification of the work procedure. Table 2 lists the confined space program elements which

are recommended (or must be considered by a qualified person, as defined by the criteria) before

entering and during work within confined spaces based on the established hazard classification.2
Page 32 - Dr. Rice Leach, Commissioner

Table 1

CONFINED SPACE CLASSIFICATION TABLE

Parameters Class A Class B Class C

Characteristics Immediately dangerous to life – rescue

procedures require the entry of more than

one individual fully equipped with life

support equipment – maintenance of

communication requires an additional

standby person stationed within the

confined space

Dangerous, but not immediately life

threatening – rescue procedures require

the entry of no more than one

individual fully equipped with life

support equipment – indirect visual or

auditory communication with workers

Potential hazard – requires no

modification of work procedures –

standard rescue procedures – direct

communication with workers, from

outside the confined space

Oxygen 16% or less

*(122 mm Hg) or

greater than 25%

*(190 mm HG)

16.1% to 19.4%

*(122 – 147 mm Hg)

or 21.5% to 25%

(163 – 190 mm Hg)

19.5 % – 21.4%

*(148 – 163 mm Hg)

Flammability

 Characteristics

20% or greater of LFL 10% – 19% LFL 10% LFL or less

Toxicity **IDLH greater than contamination level,

referenced in 29 CFR Part 1910 Sub

Part Z – less than **IDLH

less than contamination level

referenced in 29 CFR Part 1910

Sub Part Z

* Based upon a total atmospheric pressure of 760 mm Hg (sea level)

** Immediately Dangerous to Life or Health – as referenced in NIOSH Registry of Toxic and Chemical Substances, 

Manufacturing Chemists data sheets, industrial hygiene guides or other recognized authorities.

NIOSH [1979]. Criteria for a recommended standard: working in confined spaces. Cincinnati, OH: U.S. Department of Health, Education, and

Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication

No. 80–106.
Page 33 - Dr. Rice Leach, Commissioner

Table 2

CHECK LIST OF CONSIDERATIONS FOR ENTRY,

WORKING IN AND EXITING CONFINED SPACES

ITEM CLASS A CLASS B CLASS C

1. Permit X X X

2. Atmospheric Testing X X X

3. Monitoring X 0 0

4. Medical Surveillance X X 0

5. Training of Personnel X X X

6. Labeling and Posting X X X

7. Preparation

Isolate/lockout/tag

Purge and ventilate

Cleaning Processes

Requirements for special equipment/tools

X

X

0

X

X

X

0

X

0

0

0

0

8. Procedures

Initial plan

Standby

Communications/observation

Rescue

Work

X

X

X

X

X

X

X

X

X

X

X

0

X

X

X

9. Safety Equipment

and Clothing

Head protection

Hearing protection

Hand protection

Foot protection

Body protection

Respiratory protection

Safety belts

Life lines, harness

0

0

0

0

0

0

X

X

0

0

0

0

0

0

X

0

0

0

0

0

0

X

 10. Rescue Equipment X X X

 11. Recordkeeping/Exposure X X

X = indicates requirement

0 = indicates determination by the qualified person

NIOSH [1979]. Criteria for a recommended standard: working in confined spaces. Cincinnati, OH: U.S. Department of Health, Education, and Welf

for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 80–106.
Page 34 - Dr. Rice Leach, Commissioner

1. Code of Federal Regulations [1997]. 29 CFR 1910.146. Washington, DC: U.S. Government

Printing Office, Federal Register.

2. NIOSH [1979]. Criteria for a recommended standard: Working in Confined Spaces. 

Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Public Health Service,

Center for Disease Control, National Institute for Occupational Safety and Health, DHEW

(NIOSH) Publication No. 80–106.

2.

3.

4.