This presentation has been prepared by CPSC staff. It has not been reviewed or approved 

by, and may not necessarily reflect the views of, the Commission.

June 3, 2014

1
Purpose: 

To help CPSC staff gain a broader 

understanding of the scope, state of the art, 

and availability of current or prototype sensor 

technologies being used to shut off gas 

heating appliances when incomplete 

combustion or dangerous levels of CO are 

detected or that are used in similar, harsh 

environments.

2
Panel Session I:

 Project Overview: Purpose, Hazard Patterns, and 

Annual CO Death Estimates

 Physiology of Carbon Monoxide Poisoning

 CPSC Staff’s CO-related Activities

 International Standards

3
Ronald Jordan, Mechanical Engineer, 

Project Manager, Gas Appliance CO Sensor Project, 

CPSC Directorate for Engineering Sciences

This presentation has been prepared by CPSC staff. It has not been reviewed or approved 

by, and may not necessarily reflect the views of, the Commission.

4
 Purpose: To investigate the use of CO and 

combustion sensors to reduce the occurrence 

of unintentional CO deaths and injuries 

caused by failure modes and mechanisms 

associated with gas appliances

 Scope: gas furnaces, boilers, wall and floor 

furnaces

5
Comparison of Annual CO Deaths Associated with Gas Furnaces, Boilers, & Wall/Floor Furnaces and Gas 

Room/Space and Portable Gas Heaters

2001-2010

2001-

2010

Consumer Product

Average 

Annual 

Estimate

Average 

Percent 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Total

Total (all consumer products1) 166.6 100% 121 181 153 168 190 180 186 178 148 161 1666

Gas Furnace (incl. Boilers, Wall/Floor 

Furnaces) 29.6 18% 33 46 28 41 11 30 33 26 18 30 296

Gas Room/Space Heaters (incl. 

Portable Gas Heaters) 18.8 11% 20 25 24 22 20 11 18 13 15 20 188

1. These deaths are non-fire related and are associated consumer products under CPSC jurisdiction. 

Source: Hnatov, Matthew, Non-Fire Carbon Monoxide Deaths Associated with the Use of Consumer Products, 2010 Annual Estimates, U.S. Consumer Product 

Safety Commission, Bethesda, MD January 2014.

Note: Table includes data for natural gas, LP-gas, and unspecified gas appliances

6
Leakage path for combustion products into 

living space: 

 Blocked flue or chimney

 Disconnected vent

 Depressurization of a small room

Coupled with incomplete combustion: 

 Inadequate combustion air (i.e., too little air)

 Over-firing (i.e., too much fuel)

 Quenching of flame (i.e., flame temperature too low)

7
Sandra Inkster, Ph.D., Physiologist/Pharmacologist, 

CPSC Directorate for Health Sciences

This presentation has been prepared by CPSC staff. It has not been reviewed or approved 

by, and may not necessarily reflect the views of, the Commission.

8
 Chemical asphyxiant gas: interferes with the body’s 

oxygen (O2) supply

 CO binds to hemoglobin (oxygen carrying protein in 

blood) >200-250x more readily than O2 and forms 

carboxyhemoglobin (COHb)

 Level of O2 deprivation increases as COHb levels 

increase 

 Brain, heart, and exercising muscle have highest O2 

demands so are most sensitive to CO poisoning effects.

9
Approximate Correlation Between Acute % COHb Levels and Symptoms 

in Healthy Adults

% COHb Symptoms

<10% No perceptible ill effects* 

10-20% Mild headache, labored breathing, decreased exercise 

tolerance

20-30% Throbbing headache, mild nausea

30-40% Severe headache, dizziness, nausea, vomiting, cognitive 

impairment

40-50% Confusion, unconsciousness, coma, possible death

50-70% Coma, brain damage, seizures, death

>70% Typically fatal

*Some studies report adverse effects in cardiac patients at 2-5% COHb 

(source: reviewed in Burton, 1996 )
Environmental

 Maximum level of CO attained in inhaled air; parts per 

million (ppm)

 Rate of increase in CO levels

 Duration of CO elevation/CO exposure

Physiological

 Breathing rate of exposed individual; influenced by 

activity level (Respiratory Minute Volume (RMV) = air 

intake in liters/minute)

 General health status of exposed individual.

11
0

10

20

30

40

50

60

70

80

0 4 8 12 16 20 24

% COHb Level

Exposure Time (hours)

Effects of CO Level, Exposure Time, and Activity Level on 

Carboxyhemoglobin (%COHb) Formation

1000 ppm CO

400 ppm CO

100 ppm CO

For each CO exposure level, the line style denotes indoor activity level represented by RMV;

dashed = sleeping (6L/min); solid = moderate level (15 L/min); dotted = high (normally short-lived bursts) 

12
 Binding of CO to hemoglobin is reversible

 CO is removed from the body via exhaled air; the 

elimination process is much slower than uptake 

 The CO half-life means time needed to reduce % 

COHb level by 50%

◦ ~4-5 hours at fresh ambient air (~21% oxygen) 

◦ ~ 80 minutes with 100% normobaric oxygen

◦ ~20-30 minutes at 100% hyperbaric oxygen (HBO)

13
 Individuals With Certain Medical Conditions

◦ Cardiac diseases– especially ischemic heart disease/coronary 

artery disease; also arrhythmias and congestive heart disease

◦ Chronic obstructive pulmonary disease (COPD)

◦ Anemias

 Infants and Young Children

◦ Have higher rate of CO uptake due to higher metabolic rate

 The Elderly

◦ Reflects high incidence of pre-existing diseased states above 

 Fetuses

◦ Fetal hemoglobin has higher affinity for CO than maternal Hb and 

will eventually attain 10-15% higher % COHb at equilibrium

14
 Variable: from complete recovery to brain-damaged, 

vegetative state, depending on CO exposure, victim’s health.

 Delayed neurological sequelae (DNS) can occur few days to 

few weeks after apparent recovery from initial CO exposure – hard to predict, more likely at higher CO exposures resulting in >20% 

COHb; does not necessarily require loss of consciousness (LOC).

 Obvious effects: e.g., paralysis, dementia, blindness, hearing 

loss, Parkinson-like muscle/gait disorders. 

 Subtle effects: e.g., emotional instability, memory loss, 

inability to concentrate - often overlooked, but negatively affects 

work and home life so can have economic, social, and personal impact 

on victims and their families. 

15
Ronald Jordan, Mechanical Engineer, 

Project Manager, Gas Appliance CO Sensor Project, 

CPSC Directorate for Engineering Sciences

This presentation has been prepared by CPSC staff. It has not been reviewed or approved 

by, and may not necessarily reflect the views of, the Commission.

16
 Participation in voluntary standards 

development and advocacy for CO alarm 

usage

 Annual CO Safety Press Release

 Product recalls

 Participation in voluntary standards 

development for gas appliances

17
 The following changes were made to the 

voluntary standards in the mid to late-1980’s 

to address CO risks:

◦ Vent Safety Shutoff System (VSSS) added to protect 

against blocked & disconnected vents in vented 

space heaters (ANSI Z21.11.1)

◦ Oxygen Depletion Safety (ODS) shutoff system 

added to protect against CO production in unvented 

space heaters (ANSI Z21.11.2)

18
 The following changes were made to the 

voluntary standards in the mid to late-1980’s 

to address CO risks:

◦ Blocked Vent Safety Shutoff (BVSS) added to protect 

against blocked vents in gas furnaces (ANSI Z21.47)

◦ Blower door interlock switch added to prevent 

combustion products from being pulled from heat 

exchanger and circulated throughout house via 

ducts (ANSI Z21.47).

19
CO Death Estimates “Before” and “After” changes to Voluntary Standards

(as a percent of all consumer product related fatalities)

*Note: In earlier years CPSC’s annual estimates did not include distinctions between gas room/space heaters and portable heaters, therefore the 

estimates for gas space heaters during the period from 1982 to 1990 may also include portable gas heaters as well.

Source: 1982-1990 data: “Non-Fire Incident Related Carbon Monoxide (CO) Deaths Estimates for 1990,” Long, Kimberly, U.S. Consumer Product 

Safety Commission, Bethesda, MD April 1994

Source: 1999-2007 data: Non-Fire Carbon Monoxide Deaths Associated with the Use of Consumer Products. 2007 annual Estimates,” Hnatov, 

Matthew, U.S. Consumer Product Safety Commission, Bethesda, MD January 2011

22%

41%

16%

14%

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

Gas Furnaces Gas Space Heaters

CO Deaths associated with gas furnaces and 

space heaters, including Portable Gas Heaters 

(as a percent of all Consumer Products) 

9-Year period of estimate 

1982-1990 (Before) 1999-2007 (After)

20
Total Estimated CO Fatalities “Before” and “After” changes to Voluntary Standards

*Note: In earlier years CPSC’s annual estimates did not include distinctions between gas room/space heaters and portable gas heaters, therefore the 

estimates for gas space heaters during the period from 1982 to 1990 may also include portable gas heaters as well.

Source: 1982-1990 data: “Non-Fire Incident Related Carbon Monoxide (CO) Deaths Estimates for 1990,” Long, Kimberly, U.S. Consumer Product Safety 

Commission, Bethesda, MD April 1994

Source: 1999-2007 data: Non-Fire Carbon Monoxide Deaths Associated with the Use of Consumer Products. 2007 Annual Estimates,” Hnatov, Matthew, 

U.S. Consumer Product Safety Commission, Bethesda, MD January 2011

535

1024

230 199

0

200

400

600

800

1000

1200

Total Annual CO Deaths Associated with Gas Furnaces 

1 2

and Space Heaters and Portable Gas Heaters

9-Year period of estimate 

1982-1990 (Before) 1999-2007 (After)

Gas Furnaces Gas Space Heaters

21
Made to ANSI Z21.47 Central Furnace 

Subcommittee (2001) and ANSI Z21/83 

Technical Committee (2002):

◦ Require a means to prevent furnace CO emissions 

from exceeding 400 ppm; or

◦ Require a means to shut down furnace if CO 

emissions exceed 400 ppm.

22
 CO shutoff testing with catalytic bead and 

mixed metal oxide semiconductor (MMOS) CO 

sensors integrated into the vent pipe of a gas 

furnace (2001) 

 CO shutoff testing with electrochemical CO 

and infrared CO2 sensors integrated into the 

vent pipe of a gas furnace (2004)

23
 Formed the ANSI Z21/83 Ad Hoc Working Group 

(AHWG) for CO/Combustion Sensors to evaluate 

feasibility of sensors for use in all vented gas 

heating appliances (2002) 

 AHWG developed a test criterion for sensors 

(2004)

 ANSI Z21/83 Technical Committee opted to not 

pursue sensor evaluation (2005) due to concerns 

that commercially available sensors:

◦ Were not durable enough to operate in gas appliance 

flue.

◦ Did not have lifespan of a gas appliance (15-20 years).

24
 Durability and longevity testing of catalytic 

bead CO and infrared CO2 sensors integrated 

into the vent pipe, flue passages, and heat 

exchanger of a gas furnace (2007-2008)

25
Standards 

Development 

Organization (SDO)

Standard Requirement

Japanese Standards 

Association (JSA)

JIS S 2109, 

Gas burning water 

heaters for domestic 

use

Shutdown appliance at ambient CO 

level = 300 ppm (based on the CO 

concentration in the combustion 

gas)

European 

Committee for 

Standardization 

(CEN) 

EN 16430, 

Combustion product 

sensing devices for 

gas burners and gas 

burning appliances

Use of combustion product sensing 

devices (CPSD) within the flue of gas 

appliances to ensure combustion 

efficiency 

26
Panel Session II:

Industry Presentations

27