TM

NIOSH HEALTH HAZARD EVALUATION REPORT 

HETA # 2003-0318-2936 

Evaluation of Two Exhaust Stack Configurations on 

Two Houseboats at Table Rock Lake, Missouri 

June 2004 

DEPARTMENT OF HEALTH AND HUMAN SERVICES 

Centers for Disease Control and Prevention 

National Institute for Occupational Safety and Health

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally

applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved.

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports

Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports
ii 

PREFACE

The Hazard Evaluation and Technical Assistance Branch (HETAB) of the National Institute for 

Occupational Safety and Health (NIOSH) conducts field investigations of possible health hazards in the 

workplace. These investigations are conducted under the authority of Section 20(a)(6) of the 

Occupational Safety and Health (OSHA) Act of 1970, 29 U.S.C. 669(a)(6) which authorizes the Secretary 

of Health and Human Services, following a written request from any employers or authorized 

representative of employees, to determine whether any substance normally found in the place of 

employment has potentially toxic effects in such concentrations as used or found. 

HETAB also provides, upon request, technical and consultative assistance to federal, state, and local 

agencies; labor; industry; and other groups or individuals to control occupational health hazards and to 

prevent related trauma and disease. Mention of company names or products does not constitute 

endorsement by NIOSH. 

ACKNOWLEDGMENTS AND AVAILABILITY OF REPORT

This report was prepared by Ronald M. Hall of HETAB, Division of Surveillance, Hazard Evaluations 

and Field Studies (DSHEFS), and Duane Hammond and Scott Earnest of the Division of Applied 

Research and Technology (DART). Desktop publishing was performed by Robin Smith. Review and 

preparation for printing were performed by Penny Arthur.

Copies of this report have been sent to the houseboat companies who participated in the evaluation, the 

Houseboat Industry Association (HIA), and the OSHA Regional Office. This report is not copyrighted 

and may be freely reproduced. The report may be viewed and printed from the following internet 

address: www.cdc.gov/niosh/hhe/hhesearch.html. Single copies of this report will be available for a 

period of three years from the date of this report. To expedite your request, include a self-addressed 

mailing label along with your written request to: 

NIOSH Publications Office 

4676 Columbia Parkway 

Cincinnati, Ohio 45226 

800-356-4674 

After this time, copies may be purchased from the National Technical Information Service (NTIS) at 5825 

Port Royal Road, Springfield, Virginia 22161. Information regarding the NTIS stock number may be 

obtained from the NIOSH Publications Office at the Cincinnati address. 

For the purpose of informing affected employees, copies of this report 

shall be posted by the employer in a prominent place accessible to the 

employees for a period of 30 calendar days.
Highlights of Health Hazard Evaluation 

Evaluation of Two Exhaust Stack Configurations on Two 

Houseboats at Table Rock Lake, Missouri

NIOSH evaluated exhaust stack performance for control of carbon monoxide (CO) on two houseboats 

from August 25 - 28, 2003, at Table Rock Lake, Missouri. 

What NIOSH Did

 We evaluated two generator exhaust stack 

designs on two houseboats, and compared 

them to side exhaust configurations. 

 We measured area CO concentrations at 

various locations on the upper and lower 

decks of the houseboats. 

 We evaluated the boats in a cove, after dark, 

and under different generator loads, 

houseboat trim angles, and environmental 

conditions (i.e., temperature and humidity). 

What NIOSH Found

 The results of this evaluation were similar to 

results from previous NIOSH exhaust stack 

evaluations. 

 BothBoth exhaust stack configurations 

performed much better than the side exhaust 

configuration (even on the upper deck). 

 The exhaust stack designs reduced mean and 

peak CO concentrations 87% to 99.9% (when 

compared to side exhaust) at the majority of 

outdoor locations on the lower stern deck. 

 The exhaust stack designs reduced mean and 

peak CO concentrations 47% to 99% (when 

compared to side exhaust) at the majority of 

upper deck locations. 

 The exhaust stack must be designed properly 

to prevent exhaust gases from being forced 

out of the water discharge (near water level). 

What the Houseboat Industry 

Association (HIA) Can Do

 Recommend that houseboats with gasoline 

powered generators be evaluated for CO 

exposures. 

 Recommend retrofitting houseboat generator 

exhaust systems with properly designed and 

operating exhaust stacks that discharge CO 

toto non-occupied areas well above the upper 

deck. 

 Recommend the use of redundant systems, 

such as exhaust stacks with cleaner burning 

engines equipped with after treatment 

devices, when they become available. 

 Recommend that the stack exhaust be clearly 

labeled to notify anyone on the houseboat to 

avoid the exhaust gases. 

 Recommend the use of warning labels to 

address hanging clothing or other items that 

might block or restrict the stack outlet, 

unauthorized stack alterations, or climbing or 

tampering with the stack. 

 Recommend labeling the water discharge 

area as a potential CO hazard area. 

What To Do For More Information:

We encourage you to read the full report. If you 

would like a copy, either ask your health and 

safety representative to make you a copy or call 

1-513-841-4252 and ask for 

 HETA Report #2003-0318-2936
iv 

Health Hazard Evaluation Report 2003-0318-2936 

Evaluation of Two Exhaust Stack Configurations on 

Two Houseboats at Table Rock Lake, Missouri 

June 2004 

Ronald M. Hall, MS, CIH 

Duane Hammond 

G. Scott Earnest, PhD, PE, CSP

SUMMARY

In response to a request from the Houseboat Industry Association (HIA) and working under an 

interagency agreement with the United States Coast Guard, the National Institute for Occupational Safety 

and Health (NIOSH) evaluated carbon monoxide (CO) exposures and engineering controls associated 

with gasoline-powered generator exhaust on houseboats. The current health hazard evaluation (HHE) is 

part of a series of studies conducted by NIOSH investigators to identify and recommend effective 

engineering controls to prevent CO poisonings on houseboats and other recreational marine vessels. 

In the Spring of 2003, the HIA sent a letter to NIOSH and the Coast Guard Office of Boating Safety 

requesting further testing of houseboats having generator exhaust stacks. HIA indicated that their 

members would provide houseboats and testing sites. HIA members were concerned that previous 

NIOSH evaluations of houseboat generator exhaust stacks failed to include all appropriate environmental 

and operational conditions. Therefore the HIA requested that additional testing be performed under the 

following conditions: 1) in a cove, 2) after dark, 3) under various generator loads, 4) at different 

houseboat trim angles, and 5) during temperature inversions. Side exhaust versus stack exhaust was also 

evaluated. 

NIOSH researchers conducted two field evaluations in August 2003. The evaluation at Lake 

Cumberland, Kentucky, was described in a separate report (NIOSH Publication No. EPHB 171-34a). The 

evaluation at Table Rock Lake, Missouri is described in this report. The houseboats evaluated at Table 

Rock Lake were provided by Fun Country Marine Industries and Sumerset Houseboats. 

The evaluation at Lake Cumberland found problems with the stack design where CO gases were 

discharged with the water on the side of the boat. Based on those results, design changes were made to 

help alleviate the problem on houseboat #2 at Table Rock Lake. The design changes included the 

removal of a 3 foot (2 inch inner diameter) section of flexible exhaust hose, and the removal of a 180o 

angle. 

This survey indicated that high temperature/high humidity environments, generator loading, and 

houseboat trim angles had relatively small effects on exhaust stack performance. 
v 

Results of this study were consistent with those of previous NIOSH exhaust stack evaluations. Both 

exhaust stacks on the two houseboats performed dramatically better than side exhaust (even on the upper 

deck of the houseboat). With the exhaust stack, results indicated a reduction of mean and peak CO 

concentrations of approximately 87% to 99.9%, when compared to results obtained with the side exhaust, 

at the majority of outside lower deck locations on both houseboats. On the upper deck of the houseboats, 

mean and peak results obtained with the exhaust stack indicated a range of reductions of approximately 

47% to 99% in the majority of upper deck locations, when compared to the side exhaust configuration. 

Based upon the results of NIOSH exhaust stack studies, investigators recommend that houseboats using 

gasoline-powered generators be evaluated for potential CO exposures and poisonings, especially near the 

lower stern deck. Houseboat manufacturers, rental companies, and owners should consider retrofitting 

their gasoline-powered generators with engineering controls to reduce the potential hazard of CO 

poisoning and death. Other engineering control options such as cleaner burning engines and aftertreatment devices are being developed, and these options could also play an important role in preventing 

future poisonings 

Properly installed exhaust stacks have performed well during all NIOSH evaluations, and 

they are successfully being used to help prevent CO poisonings on hundreds of 

houseboats across the U.S. During this evaluation, the exhaust stacks performed well 

under a variety of environmental and operational conditions. 

Keywords: SIC Code: 4493 (Establishments primarily engaged in operating marinas and which perform 

incidental boat repair) carbon monoxide, houseboats, boats, exhaust stack, side exhaust
Table of Contents 

Preface..........................................................................................................................................................ii

Acknowledgments and Availability of Report..........................................................................................ii

Highlights of Health Hazard Evaluation .................................................................................................iii

Summary.....................................................................................................................................................iv

Introduction.................................................................................................................................................1

Background .................................................................................................................................................1

Methods........................................................................................................................................................2

Description of the Houseboats ...............................................................................................................2

Description of the Evaluation Equipment ............................................................................................2

Description of Procedures ......................................................................................................................3

Evaluation Criteria .....................................................................................................................................3

Carbon Monoxide (CO)..........................................................................................................................4

Results ..........................................................................................................................................................5

Results of Air Sampling with ToxiUltra CO Monitors........................................................................5

Stack vs. Side exhaust Lower Deck CO Results...............................................................................5

Stack vs. Side Exhaust Upper Deck CO Results ..............................................................................6

Stack Exhaust CO Results (Conditions 2, 4, and 5).........................................................................6

Gas Emissions Analyzer and Detector Tube Results.......................................................................7

Wind and Stack Velocity Measurements ..........................................................................................7

Ambient Temperature and Relative Humidity ................................................................................8

Discussion and Conclusions .......................................................................................................................8

Stack Exhaust..........................................................................................................................................8

Stack Design and Performance..............................................................................................................8

Recommendations.......................................................................................................................................9
Health Hazard Evaluation Report No. 2003-0318-2936 Page 1 

INTRODUCTION

On July 8, 2003, the National Institute for 

Occupational Safety and Health (NIOSH) 

received a request from the Houseboat Industry 

Association (HIA) to evaluate parameters related 

to exhaust stack performance and control of 

carbon monoxide (CO) exposures on houseboats 

at Table Rock Lake, Missouri. These 

parameters included high temperature/high 

humidity environments, temperature inversions, 

generator loading, and houseboat trim angles. 

The exhaust stack evaluations were conducted 

on two houseboats (each equipped with exhaust 

stack systems connected to gasoline-powered 

generators) from August 25 - 28, 2003. 

Investigations of CO-related poisonings and 

deaths on houseboats were initially conducted at 

Lake Powell, Arizona, in September and 

October 2000, involving representatives from 

NIOSH, U.S. Coast Guard, U.S. National Park 

Service (USNPS), Department of Interior, and 

Utah Parks and Recreation. These investigations 

measured hazardous CO concentrations on 

houseboats.1

 Some of the severely hazardous 

situations identified during the early studies 

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]). 

 Measurements of personal CO exposure 

during boat maintenance activities indicated 

that employees may be exposed to hazardous 

concentrations of CO. 

Epidemiological investigations have discovered 

that from 1990 through 2003, 165 boat-related 

CO poisonings occurred on Lake Powell near 

the border of Arizona and Utah. One-hundredthirteen of the poisonings occurred on 

houseboats, and 104 of these poisonings were 

attributable to generator exhaust alone. Ten of 

the 113 houseboat-related CO poisonings 

resulted in death.2

 Five-hundred and three CO 

poisonings related to recreational boats have 

been identified across the United States and that 

number continues to increase (493 of these 

poisonings occurred between 1990–2003; 66 

occurred in the 1980’s; and 44 have no specific 

date).2

BACKGROUND

Engineering control studies of these exhaust 

stacks began in February 2001 at Lake Powell in 

Arizona, and Lake Cumberland in Somerset, 

Kentucky.3,4 These studies demonstrated that an 

exhaust stack extending nine feet above the 

houseboat’s upper deck dramatically reduced the 

CO concentrations on and near the houseboat. 

A meeting was convened to address the CO 

hazard by the U.S. Coast Guard, Office of 

Boating Safety, Recreational Boating Product 

Assurance Division on May 3, 2001, in 

Lexington, Kentucky. This meeting was 

attended by houseboat manufacturers, marine 

product manufacturers, government 

representatives, and others. Following the 

meeting, NIOSH researchers were asked to 

evaluate the performance of a new prototype 

emission control device (ECD) and an 

interlocking device and to conduct further 

evaluations of the stack exhaust system. These 

evaluations were conducted in June 2001 at 

Callville Bay Marina, Nevada. These studies 

indicated that although the ECD, interlock, and 

stack exhaust system each performed well, 

longer term testing of the ECD should be 

conducted.5,6 Concerns were also expressed 

regarding potential use of the safety interlock as 

a primary control option. 

Following the June 2001 evaluations at Callville 

Bay Marina, Nevada, an interagency agreement 

was signed between the U.S. Coast Guard, 

Office of Boating Safety and the NIOSH, 

Division of Applied Research and Technology 

(DART), to conduct further field evaluations and 

computational fluid dynamics (CFD) modeling 
Page 2 Health Hazard Evaluation Report No. 2003-0318-2936 

of engineering controls for CO on houseboats 

and other marine vessels. 

In October 2002, an additional study was 

conducted at Callville Bay Marina, Nevada, to 

evaluate the performance of the exhaust stack 

and two production ECDs that had been installed 

and used on gasoline-powered generators for 

several thousand hours. Results from the study 

indicated some complications with the long-term 

performance of the production ECD.7

 

Following the October 2002 evaluations at Lake 

Mead, Nevada, NIOSH and the U.S. Coast 

Guard held a workshop at Annapolis, Maryland. 

Following this workshop, the HIA requested 

additional testing of the exhaust stack. This 

report provides background information and 

describes the evaluation methods, results, 

conclusions, and recommendations from that 

testing. 

METHODS

Measurements of CO and other exhaust gases, 

ventilation, and wind-velocity were collected on 

two houseboats. Data were collected to evaluate 

the effectiveness of the exhaust stacks in 

reducing CO concentrations. The evaluations 

took place in a cove, during the day, overnight, 

in high temperatures and humidities, and under 

various generator loads and houseboat trim 

angles. 

Description of the Houseboats 

Houseboat #1:: 2000 Fun Country Marine 

Houseboat with Vertical Exhaust Stack (see 

Figure 1) 

Engines: TwoTwo 150 hp Evinrude Ficht 

outboard engines 

Generator: 15 Kw Kohler gas generator 

Approximate dimensions of houseboat: 67 ft. 

X 14 ft. 

Exhaust Configuration: Centek Combo-Sep® 

muffler/gas/water separator to straight 

vertical exhaust stack approximately 9 feet 

above upper deck and starboard side water 

drain (at water level). 

Houseboat #2:: 2002 Sumerset Houseboat 

with Flag Pole Exhaust Stack (see Figure 2) 

Engines: TwoTwo 5.0L MPI Mercruiser 

engines with Bravo II out drive 

Generator: 20 kw Westerbeke gas generator 

Approximate dimensions of houseboat: 87 ft. 

X 18 ft. 

Exhaust Configuration: Centek Combo-Sep® 

muffler/gas/water separator to flag pole 

exhaust stack approximately 6 feet above 

upper deck and port side water drain (at water 

level). 

The generators on the houseboats provided 

electrical power for air conditioning, kitchen 

appliances, entertainment systems, navigation, 

communications equipment, etc. The gasoline 

generators were housed in the engine 

compartment beneath the stern deck. 

When generators are used on houseboats, the hot 

exhaust gases from the generators are injected 

with water near the end of the exhaust manifold 

in a process commonly called “water-jacketing.” 

Water-jacketing is used for exhaust cooling and 

noise reduction. Because the generator sits 

below the waterline, the water-jacketed exhaust 

passes through a lift muffler that further reduces 

noise and forces the exhaust gases and water up 

and out through a hole at the side of the boat. 

On boats with exhaust stacks, the water-jacketed 

exhaust passes through a muffler/gas/water 

separator (Figure 3) which is designed to route 

the exhaust gases up through the stack while the 

water flows out near the water line at the side of 

the boat. Inside the water separator, exhaust 

gases are physically mixed with cooling water. 

For an exhaust stack to function properly, the 

cooling water and the exhaust gases must be 

separated. The efficiency of the separation 

process is important to prevent water from 

entering the stack. Also, the balance of the 

resistance to flow must be minimized at the 

stack and the water drain outlet paths. 

Description of the Evaluation 

Equipment 

Emissions from the generator were characterized 

using a Ferret Instruments (Cheboygan, 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 3 

Michigan) Gaslink LT Five Gas Emissions 

Analyzer. This analyzer measures CO, carbon 

dioxide (CO2), hydrocarbons, oxygen (O2), and 

nitrogen oxides (NOx). CO, CO2, and O2, are 

expressed as percentages while hydrocarbons 

and NOx are expressed in ppm. [One percent of 

contaminant is equivalent to 10,000 ppm.] 

COCO COconcentrations were also measured 

directly in the generator exhaust with detector 

tubes [Draeger A.G. (Lubeck, Germany) CO, 

CH 29901– range 0.3% (3,000 ppm) to 7% 

(70,000 ppm)]. 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. 

Wind velocity measurements were gathered each 

minute during the air sampling using an 

omnidirectional ultrasonic anemometer (Gill 

Instruments Ltd., Hampshire, United Kingdom). 

This instrument uses a basic time-of-flight 

operating principle that depends upon the 

dimensions and geometry of an array of 

transducers. Transducer pairs alternately 

transmit and receive pulses of high frequency 

ultrasound. The time-of-flight of the ultrasonic 

waves is measured and recorded, and this time is 

used to calculate wind velocities in the X-, Y-, 

and Z-axes. This instrument is capable of 

measuring wind velocities up to 45 meters per 

second (m/sec) and taking 100 measurements 

per second. 

Air velocity exiting the exhaust stacks was 

evaluated using a VelociCalc Plus Model 8360 

air velocity meter (TSI Inc., St. Paul, 

Minnesota). The velocity readings were 

collected at the face of the exhaust stack. 

Velocity influences the dispersion of exhaust 

gases into the environment which can affect 

exposure potential. 

Description of Procedures 

 

The evaluation was performed over a four-day 

period using five generator test conditions as 

requested by the HIA. On the last day of the 

evaluation, an additional test condition was 

evaluated on houseboat #2 (Condition #6). Each 

test condition was performed on Table Rock 

Lake. Details concerning the test conditions are 

given below: 

1) Generator exhausting through the side 

exhaust terminus without a load on the 

generator and with no extra weight on the 

back of the boat. 

2) Generator exhausting through the exhaust 

stack with a load on the generator and no 

extra weight on the back of the boat. 

3) Generator exhausting through the exhaust 

stack without a load on the generator and with 

no extra weight on the back of the boat. 

4) Generator exhausting through the exhaust 

stack with a load on the generator and with 

the extra weight (on houseboat #1 extra 

weight was provided by filling the 300-gallon 

hot tub [approximately 2490 pounds], located 

on the rear center of the top deck, and on 

houseboat #2 extra weight was provided by 

placing sand bags, weighing a total of 

approximately 500 pounds, on the back swim 

platform). 

5) Generator exhausting through the exhaust 

stack without a load on the generator and with 

the extra weight on the back of the boat. 

 

6) Generator exhausting through the side 

exhaust terminus with a load on the generator 

and with extra weight on the back of the boat 

(conducted the last day of the evaluation on 

Houseboat #2). 

 

Typical sampling locations for the ToxiUltra 

real-time CO monitors on the lower and upper 

decks of the houseboats, designated with 

pentagons, are shown in Figure 4. Several 

monitors were placed on the boats’ stern swim 

platforms because people commonly enter and 

exit the water via this structure. 

EVALUATION CRITERIA
Page 4 Health Hazard Evaluation Report No. 2003-0318-2936 

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, a 

pre-existing medical condition, and/or a 

hypersensitivity (allergy). 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. Also, some substances are absorbed by 

direct contact with the skin and mucous 

membranes, and thus potentially increases the 

overall exposure. 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),8

 (2) the American Conference of 

Governmental Industrial Hygienists’ (ACGIH®) 

Threshold Limit Values (TLVs®),9

 and (3) the 

U.S. Department of Labor, Occupational Safety 

and Health Administration (OSHA) Permissible 

Exposure Limits (PELs).10 Employers are 

encouraged to follow the OSHA limits, the 

NIOSH RELs, the ACGIH TLVs, or whichever 

are the more protective criteria. 

OSHA requires an employer to furnish 

employees a place of employment that is free 

from recognized hazards that are causing or are 

likely to cause death or serious physical harm 

[Occupational Safety and Health Act of 1970, 

Public Law 91–596, sec. 5(a)(1)]. Thus, 

employers should understand that not all 

hazardous chemicals have specific OSHA 

exposure limits such as PELs and short-term 

exposure limits (STELs). An employer is still 

required by OSHA to protect their employees 

from hazards, even in the absence of a specific 

OSHA PEL. 

A time-weighted average (TWA) exposure 

refers to the average airborne concentration of a 

substance during a normal 8- to 10-hour 

workday. Some substances have recommended 

STEL or ceiling values which are intended to 

supplement the TWA where there are 

recognized toxic effects from higher exposures 

over the short-term. 

Carbon Monoxide (CO) 

Occupational criteria for CO exposures are 

applicable to USNPS and concessionaire 

employees. The occupational exposure limits 

noted below are designed for working 

populations and should not be used for 

interpreting general population exposures (such 

as visitors engaged in boating activities). The 

general public includes the very young, very old, 

and individuals that may have preexisting health 

conditions. 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 (when oxygen is displaced 

on the oxygen-carrying molecule known as 

hemoglobin with carbon monoxide [COHb]). 

Standards relevant to the general population take 

these factors into consideration, and are listed 

following the occupational criteria. 

The NIOSH REL for occupational exposures to 

CO in air is 35 ppm for full shift TWA exposure, 

and a ceiling limit of 200 ppm, which should 

never be exceeded.8

 The NIOSH REL of 

35 ppm is designed to protect workers from 

health effects associated with COHb levels in 

excess of 5%.11 NIOSH has established the 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 5 

IDLH value for CO of 1,200 ppm.12 The 

ACGIH recommends an 8-hour TWA TLV for 

occupational exposure to CO of 25 ppm.9

 The 

OSHA PEL for CO is 50 ppm for an 8-hour 

TWA exposure.10

Health Criteria Relevant to the General 

Public 

The U.S. Environmental Protection Agency 

(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 1-hour average.13 The NAAQS for 

CO was established to protect “the most 

sensitive members of the general population.” 

The World Health Organization (WHO) has 

recommended guideline values and periods of 

TWA exposures related to CO exposure in the 

general population.14 WHO guidelines are 

intended to ensure that COHb levels do not 

exceed 2.5% when a normal subject engages in 

light or moderate exercise. Those guidelines 

are: 

 87 ppm for 15 minutes 

 52 ppm for 30 minutes 

 26 ppm for 1 hour 

 9 ppm for 8 hours 

RESULTS

Results of Air Sampling with 

ToxiUltra CO Monitors 

Real-time CO monitoring results on the lower 

deck of the houseboats are shown in Figures 5 

and 6. Real-time CO monitoring results on the 

upper deck (monitor location is near the exhaust 

stacks) of the houseboats are shown in Figures 7 

and 8. CO concentrations on the stern deck and 

swim platform were very low for the vertical 

stack (houseboat #1) and flagpole stack 

(houseboat #2), while side exhaust produced 

high concentrations (Figures 5 and 6). The peak 

CO value (on the lower level back deck of 

houseboat #1) for the side exhaust configuration 

was beyond the instrument range for the 

ToxiUltra CO monitor and indicated a peak 

concentration greater than 1000 ppm (the IDLH 

value is 1,200 ppm for CO). The peak CO value 

for the side exhaust configuration on houseboat 

#2 (on the lower level port side of the swim 

platform) indicated a peak concentration of 742 

ppm. The CO concentrations on the top deck 

near the exhaust stacks of both houseboats 

(Figure 7 and Figure 8) indicated higher CO 

concentrations with the side exhaust 

configuration (under conditions of no generator 

load and no extra weight) than the stack exhaust 

configuration. The summary statistics for all of 

the ToxiUltra monitors are provided in Tables I 

through VIII. 

Stack vs. Side exhaust Lower 

Deck CO Results 

The stack and side exhaust CO data collected on 

August 25, 2003, for houseboat #1 indicated CO 

mean reductions of approximately 87% to 99% 

with the vertical stack exhaust as compared to 

side exhaust on all outside locations at the lower 

back deck (see Table I). Peak CO reductions 

ranged from 91% to 99.4% with the stack 

exhaust (when compared to the side exhaust 

configuration). CO data collected on August 

25th inside the boat (kitchen area) did not 

indicate a large difference in mean and peak 

concentrations of CO with the two different 

exhaust configurations. CO levels near the 

water and side exhaust discharge exceeded the 

CO monitor’s scale (>1000 ppm) with the side 

exhaust configuration. The CO levels measured 

at the water discharge area indicated a mean of 

0.2 ppm, and a peak level of 6 ppm with the 

stack exhaust configuration. 

The stack and side exhaust CO data collected on 

August 26, 2003, for houseboat #1 indicated CO 

mean reductions of approximately 89% to 97%, 

and CO peak reductions of approximately 93.5% 

to 98% with the vertical stack exhaust as 

compared to side exhaust on all outside locations 

on the lower back deck, with the exception of 

the port swim platform location (see Table I). 

The port swim platform location indicated a 

mean CO concentration of 2.6 ppm for the side 

exhaust and 3 ppm for the stack exhaust. Peak 

CO levels on the port swim platform were 3 ppm 
Page 6 Health Hazard Evaluation Report No. 2003-0318-2936 

with side exhaust and 2 ppm with the stack 

exhaust. 

The flag pole stack and side exhaust CO data 

collected on August 27, 2003, for houseboat #2 

indicated CO mean reductions of approximately 

97.8% to 99.9% with the flag pole stack exhaust 

as compared to side exhaust on all outside 

locations on the lower back deck (see Table II). 

CO data collected on August 27th inside the boat 

(back bedroom area), indicated reductions of 

33% to 63% of the mean CO values, and 78% to 

89% reductions in the peak CO values with the 

flag pole stack versus the side exhaust 

configuration (see Table II). 

The flag pole stack and side exhaust CO data 

collected on August 28, 2003, for houseboat #2 

indicated CO mean reductions of approximately 

90% to 99% with the flag pole stack exhaust as 

compared to side exhaust on all outside locations 

on the lower back deck (see Table II). Stack 

exhaust peak CO levels collected on August 28th

indicated reductions ranging from 92% to 99% 

(when compared to the side exhaust 

configuration) at lower deck outside locations. 

CO data collected inside the boat (back bedroom 

area) indicated similar mean and peak CO values 

for the two exhaust configurations (see Table II).

Stack vs. Side Exhaust Upper 

Deck CO Results 

On August 25, 2003, upper deck CO mean 

concentrations on houseboat #1 indicated 

reductions of approximately 95% to 99% when 

using the exhaust stack as compared to the side 

exhaust configuration (see Table III). Peak CO 

measurements on August 25th indicated that the 

stack reduced CO peak levels by 97% to 99% on 

the upper deck locations when compared to the 

side exhaust configuration. On August 26, 

2003, CO measurements on houseboat #1 

indicated that the stack reduced mean CO levels 

on the upper deck by approximately 76% to 99% 

in all locations except the top deck bar location. 

The mean CO concentrations at the top deck bar 

were low and similar for both exhaust 

configurations. Peak CO levels on the upper 

deck of houseboat #1 collected on August 26th, 

indicated reductions of 81% to 99% (with the 

use of the exhaust stack as compared to the side 

exhaust configuration) in all locations except the 

top deck bar location. Peak CO levels at the top 

deck bar location were low and similar for both 

exhaust configurations. 

, 2003Upper deck CO measurements obtained 

on houseboat #2 on August 28, 2003, indicated 

that the stack reduced mean CO levels on the 

upper deck by approximately 47% to 97%, and it 

reduced peak CO levels approximately 83% to 

97% (as compared to the side exhaust 

configuration) in all locations. On the starboard 

side top deck location, an accurate percent 

reduction could not be calculated because CO 

was not detected in this location with the stack 

exhaust configuration (see Table IV). 

Stack Exhaust CO Results 

(Conditions 2, 4, and 5) 

Tables V-VIII list upper and lower deck CO 

results for houseboat #1 and #2 when usingusing 

the exhaust stack. The data listed in these tables 

was collected under the test configurations of 2, 

4, and 5. The highest mean CO concentration on 

the upper deck of houseboat #1 was collected at 

the port rear side location near the exhaust stack 

which indicated a mean of 6.4 ppm (under 

condition 2). The highest CO peak of 263 ppm 

was also measured at the port rear side location 

(under condition #4). The CO means on the 

upper deck of houseboat #1 ranged from 0.02 – 

6.4 ppm, and the peak CO measurements ranged 

from 1 ppm – 263 ppm (see Table V). 

The highest mean CO concentration on the 

lower deck of houseboat #1 was 20 ppm. This 

mean CO concentration was collected at the 

water discharge location on the starboard side of 

the back deck. All other locations on the lower 

deck indicated CO mean concentrations ranging 

from 0.06 ppm to 5.5 ppm. The highest CO 

peak concentration of 480 ppm was measured on 

the starboard swim platform. This peak level 

may be a result of the propulsion engine on a 

recreational boat pulling up to the houseboat. 

All other peak CO levels on the lower deck of 

houseboat #1 ranged from 1 ppm to 95 ppm (see 

Table VI). 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 7 

The upper deck CO statistics for Houseboat #2 

with the flagpole design are listed in Table VII. 

The highest CO mean of 7 ppm was measured at 

the top deck port side location near the stack. 

The mean CO concentrations on the upper deck 

of houseboat #2 ranged from 0.05 ppm to 7 ppm 

(under testing conditions 2, 4, and 5). The peak 

CO measurements obtained on the upper deck 

indicated the highest peak was 72 ppm and was 

measured on the port side top deck location 

(near stack). The peaks on the upper deck of 

houseboat #2 ranged from 1 ppm to 72 ppm. 

Lower deck CO statistics for houseboat #2 under 

the testing conditions of 2, 4, and 5 are listed in 

Table VIII. The highest CO mean of 20 ppm 

was obtained at the sliding door location. The 

means on the lower deck ranged from 0.3 ppm 

to 20 ppm. The highest two CO peak 

measurements of 518 ppm and 212 ppm were 

measured at the water discharge area (the 

monitor was hanging over the side of the boat 

near the water discharge). These measurements 

were collected during the first run of the day at 

the beginning of the measurement periods. The 

water combo separator may not have been 

operating properly due to being empty (the 

separator may not have been filled with water). 

If the water separator is not operating as 

designed CO gases may exit out of the water 

discharge outlet (where the side exhaust 

configuration discharges combustion gases). 

After the system operated for approximately 5 to 

10 minutes the CO levels lowered and resulted 

in mean CO concentrations of 13.7 ppm and 

13.8 ppm (see Table VIII). The peak CO levels 

for the other lower deck locations on houseboat 

#2 ranged from 5 ppm to 131 ppm. 

Gas Emissions Analyzer and 

Detector Tube Results 

Gas emissions analyzers and detector tubes were 

used to characterize CO concentrations in and 

near the exhaust stack and near the water and 

side exhaust discharge area. This equipment 

was used because it is capable of reading higher 

CO concentrations than the ToxiUltra CO 

monitors which have an upper limit of 

approximately 1,000 ppm. The emissions 

analyzer indicated that CO concentrations 

measured directly in the exhaust stack of 

houseboat #1 ranged from approximately 6% 

(60,000 ppm) to 8.6% (86,000 ppm), and 

detector tube results ranged from approximately 

6.5% (65,000 ppm) to >7% (70,000 ppm [upper 

limit of detector tube]). The emission analyzer 

also indicated CO concentrations on houseboat 

#1 ranged from approximately 0.01% (100 ppm) 

to 0.3% (3,000 ppm) 6 inches away from the 

water and CO discharge area with the side 

exhaust configuration. CO detector tube results 

obtained at this location (6 inches away from 

water and CO discharge) with the side exhaust 

configuration ranged from approximately 150 

ppm to 3,000 ppm. 

The emissions analyzer indicated that CO 

concentrations measured directly in the exhaust 

stack of houseboat #2 ranged fromfrom 

approximately 5% (50,000 ppm) to 7.68% 

(76,800 ppm), and detector tube results ranged 

from approximately 2.8% (2,800 ppm taken at 

edge of stack and not directly in the stack) to 

>7% (70,000 ppm [upper limit of detector 

tube]). A CO detector tube result obtained on 

houseboat #2 at approximately 6 inches away 

from the water and CO discharge area (with the 

side exhaust configuration) indicated a 

concentration of 2% (20,000 ppm). 

Wind and Stack Velocity 

Measurements 

Wind velocity measurements were gathered 

during the survey with an ultrasonic 

anemometer. All data were gathered while the 

houseboats were stationary. All of the testing 

occurred in a cove where the boats were oriented 

in different directions. An attempt was made to 

position the boats in a manner such that wind 

was moving from the stern of the houseboat 

(near the CO emission sources) toward the bow 

of the houseboat to establish near worst case 

testing scenarios. 

A summary of wind velocity data is shown in 

Table IX. This table lists the houseboat bearing, 

average wind speed and direction, and standard 

deviations. As shown in the table, the first 

houseboat was oriented at 210E SW, and the 
Page 8 Health Hazard Evaluation Report No. 2003-0318-2936 

second houseboat was located at 65E NE. 

Average wind direction ranged from 126E SE to 

244E SW. Average wind speeds ranged from 

0.4 m/sec to 1.9 m/sec. 

Velocity measurements of exhaust from the 

stack on houseboat #1 indicated an average face 

velocity of 730 fpm. The flagpole stack on 

houseboat #2 indicated an average face velocity 

of 3340 fpm. The temperature and humidity 

measurements collected in the flagpole exhaust 

stack on houseboat #2 indicated temperatures 

between 99 °F and 100 °F, and humidity levels 

between 54% and 55%. 

Ambient Temperature and Relative 

Humidity 

A summary of the ambient temperature and 

relative humidity data is shown in Table X. 

Ambient temperatures over the sampling period 

ranged from 68.5 °F to 99.1°F and relative 

humidity (RH) ranged from 36.5% to 100%%. 

Humidity was lowest on Tuesday (8/26/03) 

during the afternoon testing. The high 

temperature over the sampling periods ranged 

from 77.5°F to 99.1°F and the low temperature 

ranged from 68.5°F to 80.6°F. The average 

temperature during each sampling period is also 

shown in the table. The lowest average 

temperature was 72.4°F on Tuesday (8/26/03) 

night and the highest average was 91.1°F on 

Monday (8/25/03). 

DISCUSSION AND 

CONCLUSIONS

The CO hazard to swimmers and occupants on 

houseboats that have gasoline-powered 

generators can be greatly reduced by retrofitting 

engineering control systems to the generators. 

Previous NIOSH studies have shown that an 

exhaust stack (that releases the CO and other 

emissions high above the upper deck of the 

houseboat in non-occupied areas) allows the 

contaminants to diffuse and dissipate into the 

atmosphere away from boat occupants.3, 6 The 

present study, requested by the HIA, evaluated 

the exhaust stacks on two houseboats on the lake 

in the afternoon (in a cove), at night, overnight, 

under a variety of generator load conditions, 

trim angles, and in high temperatures and 

humidities. Results from the stack testing do not 

appear to indicate a noticeable difference 

between CO concentrations and different 

environmental conditions. 

Stack Exhaust 

Data gathered when the houseboats were 

stationary in the cove indicated that the exhaust 

stack performed well and kept CO 

concentrations on both decks of the houseboat 

below life threatening levels. These tests also 

indicate that uncontrolled exhaust from a 

gasoline-powered generator using side exhaust 

close to the water can result in potentially life 

threatening CO levels. 

While results obtained with the stack are a 

dramatic improvement when compared to side 

exhaust, further reductions in CO concentrations 

could be achieved by extending the stack height 

and ensuring that static pressure in the stack 

does not force any exhaust gases out through the 

water outlet. To achieve lower CO 

concentrations on a houseboat, it is important 

that the exhaust stack, water separator, and 

associated piping and hoses be designed and 

installed properly. This can be accomplished by 

increasing stack diameter, reducing the length of 

the total stack run from the water separator, and 

eliminating unnecessary elbows. Another 

modification that could improve performance is 

to eliminate horizontal runs which can allow 

water to collect and obstruct flow, rather than 

draining back to the water separator. 

Stack Design and Performance 

A stack exhaust evaluation conducted at Lake 

Cumberland, Kentucky, found problems with the 

design where CO gases were discharged out 

with the water on the side of the boat. Design 

changes and recommendations on the stack were 

made to reduce this problem.15 The exhaust 

stack evaluated on Houseboat #2 was modified 

prior to our evaluation to help alleviate potential 

problems with the stack design noticed during 

the previous Lake Cumberland survey. The 

design changes made to the stack on houseboat 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 9 

#2 included the removal of a 3 foot (2 inch inner 

diameter) section of flexible exhaust hose, and 

the removal of a 180o angle. The angle was 

removed by placing the gas discharge on the 

opposite side of the combo separator. 

If the stack exhaust is not designed properly, the 

performance could be hindered. Rather than 

hazardous exhaust gases passing through the 

stack to a height well above the upper deck, high 

static pressure in the stack could force exhaust 

gases to pass out the side terminus near the 

water line. Increasing the number of elbows and 

the distance that the exhaust gases must travel 

increases the frictional and fitting losses in the 

pipe system and requires a higher initial velocity 

pressure to accelerate the same volume of 

exhaust through the same diameter of pipe. 

Horizontal runs should be avoided while still 

maintaining an appropriate vertical height above 

the upper deck. Other factors affecting static 

pressure in the stack include the inside diameter 

of the pipe and the roughness of the inside wall 

of the pipe. All of these combined factors 

account for increased pressure in the pipe 

system, and if high enough can be equated to 

plugging or sealing the end of the stack. Since 

exhaust gases and fluid flow will travel the path 

of least resistance, careful attention should be 

made to determine what necessary pressure 

differences are required to balance out the 

exhaust system. In addition to proper stack 

design, proper design of the water outlet and 

water separator is necessary to prevent water 

from traveling up the stack. 

The velocity pressure method illustrated in the 

Industrial Ventilation Manual16 provides a 

technique for performing calculations to help 

design the exhaust stack system. The method is 

based on the fact that all frictional and dynamic 

(fitting) losses in ducts are functions of velocity 

pressure and can be calculated by a loss 

coefficient multiplied by the velocity pressure. 

Figure 5-11 of the ventilation manual provides a 

calculation spreadsheet for performing velocity 

pressure calculations and sample calculations for 

non-standard conditions.16 It is important to 

point out that the system design considers the 

conditions at initial start-up and installation. 

The cumulative static pressure in the exhaust 

stack can be found by totaling the duct losses 

and losses from velocity increase or any other 

losses. If the resulting cumulative static 

pressure is too high, the system parameters can 

be decreased by changing the parameters that 

create losses to balance the system with the 

water outlet pressure. While multiple methods 

can be used to increase the pressure on the water 

side, efforts should focus on reducing static 

pressure in the stack to prevent excessive 

backpressure on the generator. 

Some manufacturers have been using a trial and 

error approach to determine the pressure 

differences between the stack and water outlet 

by altering the input variables such as pipe 

diameter, number of elbows, and overall length 

to arrive at a balance of the exhaust system. 

Manufacturers should be careful to do extensive 

testing and verify the system is in balance at 

multiple generator load conditions and that 

exhaust gas bubbles (indicating the presence of 

exhaust gases in the water discharge) are not 

present at the water outlet during operation of 

the generator. Manufacturers should perform 

CO testing on houseboats equipped with stacks 

to insure that the exhaust gases are going 

through the stack and are discharged in nonoccupied areas well above the top deck. 

Manufacturers are also encouraged to test CO 

levels at the water discharge area to make sure 

CO gases are not being discharged with the 

water. 

RECOMMENDATIONS

The following recommendations are provided to 

reduce CO concentrations near houseboats and 

provide a safer and healthier environment. 

1) All manufacturers/owners/users of houseboats 

that use gasoline-powered generators should be 

aware of the location of the exhaust terminus. 

Based on data from numerous NIOSH field 

surveys, NIOSH investigators recommend that 

houseboats with gasoline-powered generators be 

evaluated for potential CO exposures and 

poisonings and retrofitted with control systems 

to reduce the potential CO hazard. 
Page 10 Health Hazard Evaluation Report No. 2003-0318-2936 

2) The CO results obtained during this 

evaluation indicated that the vertical exhaust 

stack and flagpole stack performed well. Based 

upon the results of this and previous NIOSH 

evaluations, NIOSH researchers believe that 

when properly designed and installed, the 

exhaust stack is a viable, low-cost, engineering 

control that can dramatically improve the safety 

of houseboat users. Manufacturers/owners/users 

of houseboats that have gasoline-powered 

generators equipped with exhaust stacks should 

routinely check their systems to ensure that they 

are properly installed and operating. If static 

pressure in the stack is too high, exhaust gases 

can be forced out of the water outlet on the side 

of the boat. If the water outlet is below the 

water line, bubbles will be visible near the water 

outlet indicating that CO and other exhaust gases 

are being released. Modifications should be 

made to any existing exhaust stacks that are not 

properly designed and/or installed. 

Modifications should be made to ensure that all 

of the exhaust gases flow through the stack. 

These changes to exhaust stacks should be made 

in consultation with the manufacturer of the 

water separator. 

3) In multiple evaluations, properly designed 

exhaust stacks have been shown to be effective 

in reducing concentrations of COCO on 

houseboats by exhausting the hazardous CO 

high above the top deck. While concentrations 

on the boat remain relatively low (with the stack 

exhaust as compared to the side exhaust), CO 

measurements taken directly at the stack outlet 

in this evaluation indicated a range of 5% to 

8.6% CO (50,000 ppm to 86,000 ppm). Because 

this concentration is 42 to 72 times greater than 

the immediately dangerous to life and health 

value for breathing zone concentrations of CO, it 

would be prudent for houseboat manufacturers 

to clearly label and identify the exhaust outlet to 

notify users or anyone on the houseboat to stay 

clear of the exhaust gases. The label should 

include warnings against actions such as 

hanging clothing or other items that might block 

or restrict the outlet, making any unauthorized 

stack alterations, or climbing on or otherwise 

tampering with the exhaust stack. If the stack is 

damaged or exhaust flow is hindered, the 

exhaust gases may be forced out the side of the 

boat with the discharge water. Therefore, it may 

also be necessary to warn users to stay clear of 

the water discharge area by labeling the water 

discharge area as a potential CO hazard. 

4) As new engineering control devices for 

reducing CO emissions and exposures are 

developed, independent testing is needed to 

ensure that these systems perform adequately. 

These future devices could utilize a variety of 

methods to reduce the hazard. Additional 

protection from CO poisoning could be gained 

by implementing multiple controls in series. For 

example, a fuel injected generator fitted with a 

properly functioning emission control device 

connected to a well designed exhaust stack will 

provide a dramatically higher level of protection 

against possible CO poisoning than a single 

control. However, all of these controls need 

independent testing and evaluation to ensure that 

they will meet the needs of the boating public 

and do not create additional hazards (i.e., fire or 

other safety hazards). 

5) A critical component of the stack system is 

the exhaust gas/water separator. This separator 

can be incorporated within the same unit with a 

muffler, or it can be a discrete separate unit. To 

obtain optimum performance and best possible 

separation of the exhaust gases and the cooling 

water, the flow of exhaust gases and water must 

be balanced. The separator uses gravity and 

centrifugal forces to obtain separation. The 

resistance to flow in the water drain from the 

separator must be adjusted to ensure that gases 

cannot enter that part of the system and the 

resistance to flow in the exhaust gas piping 

(stack) must be designed to prevent the water 

level within the separator from rising to a point 

where it can be drawn into the exhaust gases. 

The optimum and proper performance of the 

separator is highly dependent on the piping 

sizing and arrangement, to and from the unit. 

The manufacturer of the separator can be very 

helpful with the system design and should be 

consulted during design of the stack and before 

final fitting of the unit(s).17
Health Hazard Evaluation Report No. 2003-0318-2936 Page 11 

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, U.S. Department of the Interior, to 

Joe Alston, Park Superintendent, Glen Canyon 

National Recreation Area, Page, Arizona. 

Denver, CO, NIOSH. 

 2. Safety Management Information 

System (SMIS) U.S. Department of the 

Interior (DOI). http://safetynet.smis.doi.gov/ 

COhouseboats.htm accessed December 2003. 

3. Dunn, KH,, Hall, RM,, McCammon, JB,, 

Earnest, GS [2001]: An Evaluation of an 

Engineering Control to Prevent Carbon 

Monoxide Poisonings of Individuals On 

Houseboats at Sumerset Custom Houseboats, 

Somerset, KY. 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. ECTB 171-26a. 

4. Earnest, GS,, Dunn, KH,, Hall, RM,, 

McCleery, R,, McCammon, JB [2001]: An 

Evaluation of an Engineering Control to Prevent 

Carbon Monoxide Poisonings of Individuals On 

and Around Houseboats. 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. ECTB 171-25a. 

5. Dunn, KH,, Earnest, GS,, McCleery, R,, 

Hall, RM,, McCammon, JB,, Jones. AL [2001]: 

Comparison of a Dry Stack with Existing 

Generator Exhaust Systems for Prevention of 

Carbon Monoxide Poisonings on Houseboats. 

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. ECTB 171-

28a. 

6. Earnest, GS,, Dunn, KH,, Hall, RM,, 

McCleery, R,, McCammon, JB [2001]: An 

Evaluation of an Emission Control Device, 

Exhaust Stack, and Interlock to Prevent Carbon 

Monoxide Poisonings of Individuals On 

Houseboats. 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. ECTB 171-27a. 

7. Earnest, GS,, Hall, RM,, Dunn, KH,, 

Hammond, DR,, Valladares, RM [2003]: An 

Evaluation of Vertical Exhaust Stacks and Aged 

Production Emission Control Devices to Prevent 

Carbon Monoxide Poisonings from Houseboat 

Generator Exhaust. 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. EPHB 171-32a. 

 8. 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. 

 9. ACGIH [2004]. 2004 TLVs® and 

BEIs®: threshold limit values for chemical 

substances and physical agents. Cincinnati, OH: 

American Conference of Governmental 

Industrial Hygienists. 

 10. CFR [1997]. 29 CFR 1910.1000. Code 

of Federal Regulations. Washington, DC: U.S. 

Government Printing Office, Office of the 

Federal Register. 

11. Kales, S N (1993). “Carbon Monoxide 

Intoxication.” American Family Physician 

48(6):1100-1104. 
Page 12 Health Hazard Evaluation Report No. 2003-0318-2936 

12. NIOSH (2000). Pocket Guide to Chemical 

Hazards and Other Databases: Immediately 

Dangerous to Life and Health Concentrations, 

DHHS (NIOSH). 

13. EPA (1991). Air Quality Criteria for 

Carbon Monoxide. Washington, DC, U.S. 

Environmental Protection Agency. 

14. World Health Organization (1999). 

Environmental Health Criteria 213 – Carbon 

Monoxide (Second Edition). WHO, Geneva. 

ISBN 92 4 157213 2 (NLM Classification: QV 

662). ISSN 0250-863X. 

15. Hammond, DR,, Earnest, GS,, Hall, RM 

[2004]: An Evaluation of Factors that might 

Influence Exhaust Stack Performance to Prevent 

Carbon Monoxide Poisonings from Houseboat 

Generator Exhaust. 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. EPHB 171-34a. 

 16. ACGIH (2001). Industrial Ventilation, A 

Manual of Recommended Practice. 24th Edition. 

Cincinnati, OH, American Conference of 

Government Industrial Hygienists. 

 17. Centek (2003). E-mail by John Ford 

regarding Wet Exhaust Systems on January 

21, 2004. Centek Industries Inc., 

Thomasville, GA. 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 13 

Figure 1. Houseboat #1. 2000 Fun Country Marine Houseboat with Vertical Exhaust Stack. 
Page 14 Health Hazard Evaluation Report No. 2003-0318-2936 

Figure 2. Houseboat #2. 2002 Sumerset Houseboat with Flag Pole Exhaust Stack. 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 15 

Generator 

Water 

outlet 

To exhaust 

Separator 

Figure 3: Simplified gas water separator configuration. 
Page 16 Health Hazard Evaluation Report No. 2003-0318-2936 

Sampling locations for ToxiUltra CO monitors 

on the lower and upper deck of the houseboats 

Figure 4: Sampling locations on the houseboats. 

9

7

Upper

Deck

Sample locations Not to Scale 

8

10

1

Lower

Deck 

 5 2

3 4

6
Health Hazard Evaluation Report No. 2003-0318-2936 Page 17 

Carbon Monoxide Concentrations on Lower 

Level Starboard Side Back Deck (Houseboat #1 

on 8/25/03)

0

200

400

600

800

1000

1200

0:00:00 0:14:24 0:28:48 0:43:12 0:57:36 1:12:00

Time (hr:min:sec)

CO Concentration 

(ppm)

Side

Exhaust

Stack

Exhaust

Figure 5. Comparison of CO concentrations on the lower level starboard side back deck of houseboat #1 

(side exhaust was located on starboard rear side of boat at water level). Under conditions of no 

generator load and no extra weight. 

Carbon Monoxide Concentrations on Lower 

Port Side Swim Platform (Houseboat #2, 8/27/03)

0

100

200

300

400

500

600

700

800

0:00:00 0:07:12 0:14:24 0:21:36 0:28:48

Time (hr:min:sec)

CO Concentration (ppm)

Side

Exhaust

Flagpole

Stack

Exhaust

Figure 6. Comparison of CO concentrations on the lower level port side swim platform of houseboat #2 

(side exhaust was located on port rear side of boat at water level). Under conditions of no 

generator load and no extra weight. 
Page 18 Health Hazard Evaluation Report No. 2003-0318-2936 

Carbon Monoxide Concentrations on Upper Deck 

near Exhaust Stack (Houseboat #1, 8/25/03)

0

20

40

60

80

100

120

140

0:00:00 0:14:24 0:28:48 0:43:12 0:57:36 1:12:00

Time (hr:min:sec)

CO Concentration 

(ppm)

Side

Exhaust

Stack

Exhaust

Figure 7. Comparison of CO concentrations on the upper level of houseboat #1 near the exhaust stack. 

 (under conditions of no generator load and no extra weight). 

Carbon Monoxide Concentrations on Upper deck 

Near Exhaust Stack (Houseboat #2, 8/27/03) 

0

50

100

150

200

250

300

350

0:00:00 0:07:12 0:14:24 0:21:36 0:28:48

Time (hr:min:sec)

CO Concentration 

(ppm)

Side

Exhaust

Stack

Exhaust

Figure 8. Comparison of CO concentrations on the upper level of houseboat #2 near the exhaust stack. 

 (under conditions of no generator load and no extra weight). 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 19 

Table I--CO Concentrations (ppm) 

Lower deck comparison on Houseboat #1 of vertical stack and side exhaust with no 

generator load and no extra weight (Conditions #1 and #3) 

HETA 2003-0318-2936 

Sample Location 

(See Figure 4) 

Vertical Stack 

8/25/03 

Condition #3 

Side Exhaust 

8/25/03 

Condition #1 

Vertical Stack 

8/26/03 

Condition #3 

Side Exhaust 

8/26/03 

Condition #1 

Slide @ breathing 

zone height 

#6 

Mean = 1.06 

Std. Dev. = 0.34 

Peak = 2 

N = 125 

Mean = 15 

Std. Dev. = 45 

Peak = 336 

N = 156 

Mean = 0.6 

Std. Dev.=2.1 

Peak = 10 

N = 32 

Mean = 17 

Std. Dev.=30 

Peak = 153 

N = 73 

Sliding door 

#2 

Mean = 2.4 

Std. Dev. = 7.6 

Peak = 51 

N = 125 

Mean = 18.4 

Std. Dev. = 62 

Peak = 555 

N = 156 

Mean = 3 

Std. Dev.=2.6 

Peak = 13 

N = 34 

Mean = 27 

Std. Dev.=75 

Peak = 563 

N = 77 

Starboard swim 

platform 

#3 

Mean = 0.61 

Std. Dev. = 0.52 

Peak = 2 

N = 123 

Mean = 49 

Std. Dev. =146 

*Peak = 1022 

N = 156 

Mean = 1.4 

Std. Dev.=3 

Peak = 13 

N = 32 

Mean = 54 

Std. Dev.=69 

Peak = 220 

N = 71 

Port swim 

platform 

#4 

Mean = 0.1 

Std. Dev. = 0.3 

Peak = 1 

N = 126 

Mean = 9 

Std. Dev.=43 

Peak = 404 

N = 154 

Mean = 3 

Std. Dev.=10 

Peak = 40 

N = 30 

Mean = 2.6 

Std. Dev.=2.9 

Peak = 14 

N = 73 

Kitchen 

#1 

Mean = 3.6 

Std. Dev. = 1.2 

Peak = 10 

N = 125 

Mean = 6.4 

Std. Dev. = 1 

Peak = 8 

N = 156 

Mean = 1.8 

Std. Dev.=0.39 

Peak = 2 

N = 34 

Mean = 2.3 

Std. Dev.=0.57 

Peak = 3 

N = 71 

Hanging on 

starboard side of 

boat near water 

discharge #5 

Mean = 0.2 

Std. Dev. = 0.86 

Peak = 6 

N = 124 

No data 

CO levels too 

high to 

measure with 

monitor 

Mean = 4.3 

Std. Dev.=6.2 

Peak = 25 

N = 33 

**Mean = 59 

Std. Dev.=169 

*Peak = 1052 

N = 74 

N= number of data points 

** - Monitor was moved onto floor of back deck to avoid burning out the CO sensor- Peak 

levels were greater than the instrument range. 

 * Peak Levels exceeded upper limit of CO instrument. 

 Std.Dev. = Standard Deviation 

 CO = Carbon Monoxide 

 ppm = parts per million 
Page 20 Health Hazard Evaluation Report No. 2003-0318-2936 

Table II--CO Concentrations (ppm) 

Lower deck comparison on Houseboat #2 of Flag Pole stack and side exhaust with no 

generator load and no extra weight (Conditions #1 and #3) for 8/27/03, and with generator 

load and extra weight (Conditions #4 and #6) for 8/28/03. 

HETA 2003-0318-2936 

Sample Location 

(See Figure 4) 

Flag Pole Stack 

8/27/03 

Condition #3 

(1847-1950) 

Flag Pole Stack 

8/27/03 

Condition #3 

(2046-2125) 

Side Exhaust 

8/27/03 

Condition #1 

Flag Pole Stack 

8/28/03 

Condition #4 

(1406-1424) 

Side Exhaust 

8/28/03 

Condition #6 

Stairs @ breathing 

zone height 

#6 

Mean = 7.5 

Std. Dev. = 5.3 

Peak = 27 

N = 126 

Mean = 5.6 

Std. Dev. = 6.2 

Peak = 30 

N = 77 

Mean = 345 

Std. Dev.= 234 

*Peak = 1061 

N = 52 

Mean = 1.4 

Std. Dev.=1.4 

Peak = 5 

N = 36 

Mean = 61 

Std. Dev.=37 

Peak = 157 

N = 25 

Starboard side 

Closet door 

#2 

Mean = 5.2 

Std. Dev. = 2.7 

Peak = 25 

N = 126 

Mean = 7.2 

Std. Dev. = 2.5 

Peak = 17 

N = 78 

Mean = 628 

Std. Dev. =360 

*Peak = 1246 

N = 50 

Mean = 9.5 

Std. Dev.=4.5 

Peak = 22 

N = 36 

Mean = 98 

Std. Dev.=75 

Peak = 278 

N = 26 

Starboard swim 

platform 

#3 

Mean = 0.73 

Std. Dev. = 0.86 

Peak = 4 

N = 126 

Mean = 2.8 

Std. Dev. =12 

Peak =71 

N = 78 

Mean = 166 

Std. Dev. =108 

Peak = 467 

N = 50 

Mean = 0.3 

Std. Dev.=0.59 

Peak = 2 

N = 36 

Mean = 94 

Std. Dev.=81 

Peak = 272 

N = 27 

Port swim 

platform 

#4 

Mean = 1.2 

Std. Dev. = 0.99 

Peak = 4 

N = 126 

Mean = 7.4 

Std. Dev. = 12 

Peak = 81 

N = 78 

Mean = 386 

Std. Dev.=208 

Peak = 742 

N = 50 

Mean = 2.3 

Std. Dev.=2.2 

Peak = 9 

N = 36 

Mean = 301 

Std. Dev.=231 

Peak = 922 

N = 27 

Back Bedroom 

(Inside Boat) 

#1 

Mean = 4.4 

Std. Dev. = 0.49 

Peak = 5 

N = 126 

Mean = 8 

Std. Dev. = 1.2 

Peak = 10 

N = 78 

Mean = 12 

Std. Dev.=12.6 

Peak = 45 

N = 51 

Mean = 5.8 

Std. Dev.=0.51 

Peak = 7 

N = 36 

Mean = 6.3 

Std. Dev.=0.45 

Peak = 7 

N = 26 

Hanging on 

starboard side of 

boat near water 

discharge #5 

Mean = 1.2 

Std. Dev. = 5.5 

Peak = 35 

N = 126 

No Data 

Collected During 

this Time Frame 

**Mean = 1094 

Std. Dev. = 2.5 

**Peak = 1099 

N = 6 

Mean = 6.9 

Std. Dev.=5.6 

Peak = 25 

N = 38 

Mean = 434 

Std. Dev.=444 

*Peak = 1110 

N = 26 

 N= number of data points 

**Monitor was shut off to avoid burning out the CO sensor- Peak levels were greater than the 

range of the instrument. 

* Peak Levels exceeded upper limit of CO instrument. 

 Std.Dev. = Standard Deviation 

 CO = Carbon Monoxide 

 ppm = parts per million 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 21 

Table III--CO Concentrations (ppm) 

Upper deck comparison on Houseboat #1 of vertical stack and side exhaust with no 

generator load and no extra weight (Conditions #1 and #3) 

HETA 2003-0318-2936 

Sample Location 

(See Figure 4) 

Vertical Stack 

8/25/03 

Condition #3 

Side Exhaust 

8/25/03 

Condition #1 

Vertical Stack 

8/26/03 

Condition #3 

Side Exhaust 

8/26/03 

Condition #1 

Top Deck Port 

Rear Side (near 

stack exhaust) 

#7 

Mean = 0.46 

Std. Dev. = 0.52 

Peak = 2 

N = 125 

Mean = 9.8 

Std. Dev. = 13 

Peak = 124 

N = 156 

Mean = 0.47 

Std. Dev.=1.2 

Peak = 5 

N = 32 

Mean = 10 

Std. Dev.=26 

Peak = 156 

N = 76 

Top Deck Center 

#9 

Mean = 0.36 

Std. Dev. = 0.48 

Peak = 1 

N = 125 

Mean = 7 

Std. Dev. = 7.7 

Peak = 63 

N = 156 

Mean = 1.3 

Std. Dev.=1.9 

Peak = 9 

N = 32 

Mean = 5.4 

Std. Dev.=9.3 

Peak = 48 

N = 77 

Top Deck Bar 

#10 

Mean = 0.2 

Std. Dev. = 0.41 

Peak = 1 

N = 123 

Mean = 3.6 

Std. Dev. =5.9 

Peak = 44 

N = 156 

Mean = 1 

Std. Dev.=1.7 

Peak = 9 

N = 32 

Mean = 1.1 

Std. Dev.=1.2 

Peak = 6 

N = 78 

 Top Deck 

Starboard side 

#8 

Mean = 0.27 

Std. Dev. = 0.44 

Peak = 1 

N = 125 

Mean = 44 

Std. Dev.=46 

Peak = 304 

N = 156 

Mean = 0.44 

Std. Dev.=0.98 

Peak = 4 

N = 32 

Mean = 38 

Std. Dev.=73.5 

Peak = 370 

N = 76 

 N= number of data points 

 Std.Dev. = Standard Deviation 

 CO = Carbon Monoxide 

 ppm = parts per million 

 
Page 22 Health Hazard Evaluation Report No. 2003-0318-2936 

Table IV--CO Concentrations (ppm) 

Upper deck comparison on Houseboat #2 of Flag Pole Stack and side exhaust with no 

generator load and no extra weight (Conditions #1 and #3) for 8/27/03, and with generator 

load and extra weight (Conditions #4 and #6) for 8/28/03. 

HETA 2003-0318-2936 

Sample Location 

(See Figure 4) 

Flag Pole Stack 

8/27/03 

Condition #3 

(1847-1950) 

Flag Pole Stack 

8/27/03 

Condition #3 

(2046-2125) 

Side Exhaust 

8/27/03 

Condition #1 

Flag Pole Stack 

8/28/03 

Condition #4 

(1406-1424) 

Side Exhaust 

8/28/03 

Condition #6 

Top Deck Port 

Rear Side (near 

Flag Pole Stack) 

#7 

Mean = 3.1 

Std. Dev. =2.4 

Peak = 11 

N = 126 

Mean = 2.6 

Std. Dev. =2.5 

Peak = 11 

N = 75 

Mean = 103 

Std. Dev. = 76 

Peak = 311 

N = 51 

Mean = 1 

Std. Dev. =1.4 

Peak = 5 

N = 38 

Mean = 34 

Std. Dev. =34 

Peak = 117 

N = 26 

Top Deck 

Center #9 

Mean = 0.53 

Std. Dev. = 0.6 

Peak = 4 

N = 126 

Mean = 0.76 

Std. Dev. = 0.66 

Peak = 4 

N = 74 

Mean =2.5 

Std. Dev. =7.8 

Peak = 45 

N = 50 

Mean = 0.42 

Std. Dev. = 0.72 

Peak = 3 

N = 38 

Mean = 15 

Std. Dev. =20 

Peak = 84 

N = 26 

Top Deck 

Bar #10 

Mean = 1.2 

Std. Dev. =0.46 

Peak = 4 

N = 126 

Mean = 7.1 

Std. Dev. = 13.9 

Peak =91 

N = 75 

Mean = 1.1 

Std. Dev.=0.35 

Peak = 2 

N = 50 

Mean = 0.58 

Std. Dev. = 0.5 

Peak = 1 

N = 36 

Mean = 1.1 

Std. Dev. =1.2 

Peak = 6 

N = 26 

Top Deck 

Starboard 

Side #8 

Mean = 0.42 

Std. Dev. = 1.4 

Peak = 8 

N = 128 

Mean = 0.4 

Std. Dev. =1.9 

Peak = 13 

N = 74 

Mean = 6.9 

Std. Dev. =11 

Peak = 54 

N = 51 

Mean = ND 

Std. Dev. =ND 

Peak = ND 

N = 38 

Mean =15 

Std. Dev. =17 

Peak = 64 

N = 26 

 N= number of data points 

 ND = CO not detected 

 Std.Dev. = Standard Deviation 

 CO = Carbon Monoxide 

 ppm = parts per million 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 23 

Table V--CO Concentrations (ppm) 

Upper deck comparison of Conditions #2, #4, and #5 for Houseboat #1 (Verticle Stack) 

HETA 2003-0318-2936 

Sample 

Location 

(See Figure 4) 

Condition #2 

8/25/03 

(1645-2051) 

Condition #2 

8/25/03 

Overnight 

(2153-0724) 

Condition #4 

8/26/03 

Condition #5 

8/26/03 

Condition #2 

8/26/03 

Top Deck Port 

Rear Side 

(near Stack) #7 

8/25/03 

Mean =6.4 

Std. Dev. = 17 

Peak = 177 

N = 489 

Mean =1 

Std. Dev. = 7 

Peak = 101 

N = 1143 

Mean = 0.8 

Std. Dev. = 8.6 

Peak = 263 

N = 1355 

Mean=0.87 

Std. Dev. =3.4 

Peak = 37 

N = 132 

Mean= 2 

Std. Dev. =1.9 

Peak = 5 

N = 80 

Top Deck 

Center #9 

8/25/03 

Mean = 1.2 

Std. Dev. = 2.9 

Peak =36 

N = 490 

Mean =0.06 

Std. Dev. = 0.29 

Peak = 4 

N = 1142 

Mean =0.96 

Std. Dev. = 1.7 

Peak =41 

N = 1352 

Mean=0.83 

Std. Dev.=0.77 

Peak =6 

N = 134 

Mean=2.4 

Std. Dev. =1.1 

Peak = 5 

N = 80 

Top Deck 

Bar #10 

8/25/03 

Mean =0.77 

Std. Dev.= 0.95 

Peak =10 

N = 490 

Mean =0.02 

Std. Dev. = 0.14 

Peak = 2 

N = 1143 

Mean = 0.37 

Std. Dev.= 0.85 

Peak = 17 

N = 1353 

Mean=0.76 

Std. Dev. = 2.7 

Peak =20 

N = 134 

Mean= 0.64 

Std. Dev. =0.48 

Peak = 1 

N = 80 

Top Deck 

Starboard 

side #8 

8/25/03 

Mean =5 

Std. Dev. = 9.9 

Peak = 97 

N = 490 

Mean =0.04 

Std. Dev. = 0.46 

Peak = 9 

N = 1142 

Mean = 0.5 

Std. Dev. = 1.6 

Peak = 35 

N = 1353 

Mean =0.3 

Std. Dev. = 0.86 

Peak =8 

N = 134 

Mean=0.56 

Std. Dev. =2.7 

Peak = 18 

N = 80 

 N= number of data points 

 Std.Dev. = Standard Deviation 

 CO = Carbon Monoxide 

 ppm = parts per million 
Page 24 Health Hazard Evaluation Report No. 2003-0318-2936 

Table VI--CO Concentrations (ppm) 

Lower deck comparison of Conditions #2, #4, and #5 for Houseboat #1 (Verticle Stack) 

HETA 2003-0318-2936 

Sample Location 

(See Figure 4) 

Condition #2 

8/25/03 

(1645-2051) 

Condition #2 

8/25/03 

Overnight ( 

2153-0724) 

Condition #4 

8/26/03 

Overnight 

Condition #5 

8/26/03 

Condition #2 

8/26/03 

Slide @ 

breathing 

zone height 

#6 

Mean =2.8 

Std. Dev. = 5.6 

Peak = 82 

N = 490 

Mean =0.5 

Std. Dev. = 0.64 

Peak = 11 

N = 1144 

Mean =0.57 

Std. Dev. = 4.3 

Peak = 95 

N = 1350 

Mean =0.4 

Std. Dev. = 0.69 

Peak = 4 

N = 136 

Mean = 0.06 

Std. Dev. =0.24 

Peak = 1 

N = 80 

Sliding door 

#2 

Mean =2.8 

Std. Dev. = 4.5 

Peak = 49 

N = 490 

Mean =0.16 

Std. Dev. = 0.94 

Peak = 17 

N = 1144 

Mean =0.71 

Std. Dev. = 1.9 

Peak = 33 

N = 1350 

Mean =0.92 

Std. Dev. = 0.74 

Peak = 4 

N = 134 

Mean = 2.7 

Std. Dev. =0.49 

Peak = 4 

N = 80 

Starboard swim 

platform 

#3 

Mean =5.6 

Std. Dev. = 32.9 

Peak = *480 

N = 492 

Mean =0.5 

Std. Dev. = 0.64 

Peak = 11 

N = 1144 

Mean =0.67 

Std. Dev. = 1.8 

Peak = 36 

N = 1350 

Mean = 0.6 

Std. Dev. =0.7 

Peak = 4 

N = 134 

Mean = 0.3 

Std. Dev. =0.5 

Peak = 1 

N = 80 

Port swim 

platform 

#4 

Mean =1.3 

Std. Dev. = 3.4 

Peak = 32 

N = 491 

Mean =0.38 

Std. Dev. = 3.3 

Peak = 70 

N = 1142 

Mean = 0.5 

Std. Dev. =1.7 

Peak = 45 

N = 1351 

Mean = 0.87 

Std. Dev. =2 

Peak = 15 

N = 134 

Mean = 0.3 

Std. Dev. =0.53 

Peak = 2 

N = 80 

Kitchen 

#1 

Mean =3.1 

Std. Dev. = 0.46 

Peak = 5 

N = 490 

Mean = 2.9 

Std. Dev. = 0.34 

Peak = 4 

N = 1144 

Mean = 2 

Std. Dev. =0.44 

Peak = 4 

N = 1351 

Mean = 1.4 

Std. Dev. =0.49 

Peak = 2 

N = 136 

Mean = 2 

Std. Dev. =0.47 

Peak = 3 

N = 82 

Hanging on 

starboard side of 

boat near water 

discharge #5 

Mean =3.2 

Std. Dev. = 9.4 

Peak = 78 

N = 492 

Mean = 0.53 

Std. Dev. = 1.3 

Peak = 10 

N = 1142 

Mean = 2.8 

Std. Dev. =5.7 

Peak = 47 

N = 1354 

Mean = 4.7 

Std. Dev. =9.6 

Peak = 56 

N = 129 

Mean = 20 

Std. Dev. =9 

Peak = 43 

N = 58 

 N= number of data points. 

 * High Peak may be a result of boat pulling up to houseboat. Peak may be from boat engine exhaust 

and may not be a result of stack emissions from generator on houseboat. 

 Std.Dev. = Standard Deviation 

 CO = Carbon Monoxide 

 ppm = parts per million 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 25 

Table VII--CO Concentrations (ppm) 

Upper deck comparison of Conditions #2, #4, and #5 for Houseboat #2 (Flag Pole Stack) 

HETA 2003-0318-2936 

Sample 

Location 

(See Figure 4) 

Condition #2 

8/27/03 

(1744-1847) 

Condition #2 

8/27/03 

(2020-2046) 

Condition #4 

8/28/03 

(1252-1333) 

Condition #5 

8/28/03 

(1333-1406) 

Condition #5 

8/28/03 

(1444-1506) 

Top Deck Port 

Rear Side (near 

Stack) #7 

8/25/03 

Mean = 3.9 

Std. Dev. =7.5 

Peak = 54 

N = 133 

Mean = 7 

Std. Dev. = 5 

Peak = 30 

N = 55 

Mean = 5.8 

Std. Dev. = 11.6 

Peak = 72 

N = 82 

Mean = 0.43 

Std. Dev. = 1.1 

Peak = 4 

N = 14 

Mean = 1 

Std. Dev. = 1.6 

Peak = 7 

N = 43 

Top Deck 

Center #9 

8/25/03 

Mean = 2.1 

Std. Dev. =8.2 

Peak = 64 

N = 132 

Mean =0.6 

Std. Dev. = 0.52

Peak = 2 

N = 56 

Mean = 6.9 

Std. Dev. = 9.6 

Peak = 68 

N = 82 

Mean = 2.9 

Std. Dev. = 7.3 

Peak = 26 

N = 16 

Mean = 0.63 

Std. Dev. = 0.79 

Peak = 3 

N = 43 

Top Deck Bar 

#10 

8/25/03 

Mean = 1.5 

Std. Dev. =1.5 

Peak = 11 

N = 133 

No Data 

Collected at this 

location During 

this Time 

Frame 

Mean = 3.2 

Std. Dev. = 7.5 

Peak = 55 

N = 82 

Mean = 0.87 

Std. Dev. = 0.35 

Peak = 1 

N = 15 

Mean = 0.73 

Std. Dev. = 0.45 

Peak = 1 

N = 44 

Top Deck 

Starboard 

side #8 

8/25/03 

Mean = 1.1 

Std. Dev. = 4 

Peak = 24 

N = 131 

Mean = 0.18 

Std. Dev. = 0.7 

Peak = 4 

N = 55 

Mean = 2.4 

Std. Dev. = 11 

Peak = 70 

N = 82 

Mean = 0.08 

Std. Dev. = 0.28 

Peak = 1 

N = 13 

Mean = 0.05 

Std. Dev. = 0.21 

Peak = 1 

N = 44 

 N= number of data points 

 Std.Dev. = Standard Deviation 

 CO = Carbon Monoxide 

 ppm = parts per million 
Page 26 Health Hazard Evaluation Report No. 2003-0318-2936 

Table VIII--CO Concentrations (ppm) 

Lower deck comparison of Conditions #2, #4, and #5 for Houseboat #2 (Flag Pole Stack) 

HETA 2003-0318-2936 

Sample Location 

(See Figure 4) 

Condition #2 

8/27/03 

(1744-1847) 

Condition #2 

8/27/03 

(2020-2046) 

Condition #4 

8/28/03 

(1252-1333) 

Condition #5 

8/28/03 

(1333-1406) 

Condition #5 

8/28/03 

(1444-1506) 

Stairs@ 

breathing zone 

height 

#6 

Mean = 2.9 

Std. Dev. = 4.7 

Peak = 29 

N = 135 

Mean = 6.8 

Std. Dev. = 5 

Peak = 26 

N = 56 

Mean = 2.6 

Std. Dev. = 9.4 

Peak = 56 

N = 82 

Mean = 1.6 

Std. Dev. = 2 

Peak = 6 

N = 12 

Mean = 0.3 

Std. Dev. = 1 

Peak = 5 

N = 46 

Sliding door 

#2 

Mean = 12.3 

Std. Dev. = 14.5 

Peak = 131 

N = 132 

Mean = 20 

Std. Dev. = 11.2 

Peak = 86 

N = 56 

Mean = 6.7 

Std. Dev. = 8.2 

Peak = 56 

N = 80 

Mean = 8.5 

Std. Dev. = 4.2 

Peak = 17 

N = 13 

Mean = 11.3 

Std. Dev. = 9.9 

Peak = 54 

N = 48 

Starboard swim 

platform 

#3 

Mean = 1.7 

Std. Dev. = 5.8 

Peak = 34 

N = 132 

Mean = 1 

Std. Dev. = 1.8 

Peak = 8 

N = 56 

Mean = 5 

Std. Dev. = 8.4 

Peak = 56 

N = 82 

Mean = 1.1 

Std. Dev. = 1.9 

Peak = 5 

N = 10 

Mean = 1.4 

Std. Dev. = 1.2 

Peak = 5 

N = 47 

Port swim 

Platform #4 

Mean = 1.5 

Std. Dev. = 5.4 

Peak = 38 

N = 132 

Mean = 15 

Std. Dev. = 6 

Peak = 32 

N = 56 

Mean = 6.7 

Std. Dev. = 6 

Peak = 25 

N = 82 

Mean = 2.3 

Std. Dev. = 2.4 

Peak = 7 

N = 12 

Mean = 6.5 

Std. Dev. = 4.4 

Peak = 18 

N = 48 

Back Bedroom 

(Inside Boat) 

#1 

Mean = 5.4 

Std. Dev. = 1.2 

Peak = 7 

N = 137 

Mean = 12.2 

Std. Dev. = 2.4 

Peak = 19 

N = 53 

Mean = 2.8 

Std. Dev. = 1.1 

Peak = 6 

N = 80 

Mean = 5.2 

Std. Dev. = 0.56 

Peak = 6 

N = 13 

Mean = 5.8 

Std. Dev. = 0.5 

Peak = 7 

N = 48 

Hanging on 

starboard side 

of boat near 

water discharge 

#5 

Mean = 13.7 

Std. Dev. = 51 

*Peak = 518 

N = 132 

No data collected 

at this location 

for this time 

period 

Mean = 13.8 

Std. Dev. = 31 

*Peak = 212 

N = 82 

Mean = 5.4 

Std. Dev. = 4.8 

Peak = 18 

N = 16 

Mean = 13.9 

Std. Dev. = 15.6 

Peak = 61 

N = 47 

N= number of data points. 

* High Peak may be a result of water combo separator filling up with water (first run of the day). 

During this process when generator is first started it may result with some CO exiting through the water 

outlet until combo separator is filled with water. If system has too much static pressure on the gas 

discharge side, CO can be emitted out of water discharge near water level. 

CO = Carbon Monoxide 

ppm = parts per million 

Std.Dev. = Standard Deviation 
Health Hazard Evaluation Report No. 2003-0318-2936 Page 27 

Table IX-- Boat Heading and Wind Velocity Data 

HETA 2003-0318-2936 

Day/Boat Houseboat 

Bearing

Average 

Wind Direction

Average 

Wind Speed 

(meters/sec)

Standard 

Deviation 

Wind Speed 

(meters/sec)

Monday afternoon 

Houseboat #1

210o 126o 1.5 m/sec 0.8 m/sec 

Monday night 

Houseboat #1

210o 239o 0.4 m/sec 0.2 m/sec 

Tuesday afternoon 

Houseboat #1

210o 133o 1.9 m/sec 1.1 m/sec 

Tuesday night 

Houseboat #1 

210o 244o 0.5 m/sec 0.3 m/sec 

Wednesday evening 

Houseboat #2

65o 135o 0.5 m/sec 0.3 m/sec 

Thursday afternoon 

Houseboat #2

65o 131o 1.5 m/sec 0.9 m/sec 
Page 28 Health Hazard Evaluation Report No. 2003-0318-2936 

Table X-- Ambient Temperature and Relative Humidity Data 

HETA 2003-0318-2936 

Day/Boat Temp 

Range 

Temp 

Avg. 

Temp 

Std. 

Dev. 

Humidity 

Range

Humidity 

Average 

Humidity 

Std. Dev. Number 

of Data 

Points 

Monday 

afternoon 

Houseboat #1

74.8 – 

97.2°F 

91.1°F 8.6 40 – 63 

%RH 

47% RH 5.9 125 

Monday night 

Houseboat #1

77 – 

96.4°F 

83.2°F 5.9 42.5 – 80 

%RH 

68% RH 11.6 861 

Tuesday 

afternoon 

Houseboat #1

71.2 – 

99.1°F 

82.9°F 10.7 36.5 – 87 

%RH 

45% RH 7.5 385 

Tuesday night 

Houseboat #1 

68.5 – 

77.5°F 

72.4°F 2.4 75 – 100 

%RH 

94% RH 6.1 908 

Wednesday 

evening 

Houseboat #2

73 – 

89.8°F 

76.8°F 6.0 52 – 86 

%RH 

68% RH 6.8 1037 

Thursday 

afternoon 

Houseboat #2

80.6 – 

90.3°F 

86°F 2.9 50.5 – 

75.5 %RH

63% RH 6.8 194 

Temp= Temperature 

 Std.Dev. = Standard Deviation 
DEPARTMENT OF HEALTH AND HUMAN SERVICES 

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