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Carbon Monoxide/Combustion Sensor Forum

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

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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.

Carbon Monoxide/Combustion Sensor Forum

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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

Carbon Monoxide/Combustion Sensor Forum

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Gas Appliance CO Sensor Project Overview

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.

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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

The Gas Appliance CO Sensor Project

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Annual CO Death Estimates

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 1666Gas Furnace (incl. Boilers, Wall/Floor Furnaces) 29.6 18% 33 46 28 41 11 30 33 26 18 30 296Gas Room/Space Heaters (incl. Portable Gas Heaters) 18.8 11% 20 25 24 22 20 11 18 13 15 20 1881. 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

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Leakage path for combustion products intoliving 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)

Hazard Patterns

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Physiology of Carbon Monoxide Poisoning

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.

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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.

Properties of Carbon Monoxide (CO)

Approximate Correlation Between % COHb Levels and Symptoms In Healthy Adults

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 )

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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.

Key Factors Affecting COHb Levels

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0 4 8 12 16 20 240

10

20

30

40

50

60

70

80

Effects of CO Level, Exposure Time, and Activity Level on Carboxyhemoglobin (%COHb) Formation

Exposure Time (hours)

% C

OH

b L

ev

el

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)

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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)

Elimination of CO from the Body

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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

Populations More Susceptible to CO Poisoning

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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.

Lasting Effects in CO Poisoning Survivors

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CPSC Staff’s CO-related Activities and International Standards

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.

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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

CPSC Staff’s CO-related Activities

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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)

Voluntary Standards Changes for Gas Space Heaters

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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).

Voluntary Standards Changes for Gas Space Heaters

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Impact of Changes to Voluntary Standards for Gas Space Heaters* & Gas Furnaces: A Comparison

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 1994Source: 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

Gas Furnaces Gas Space Heaters0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

22%

41%

16%

14%

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

9-Year period of estimate

CO

Death

s a

ssocia

ted w

ith g

as f

urn

aces

and s

pace h

eate

rs,

inclu

din

g P

ort

able

G

as H

eate

rs (

as a

perc

ent

of

all C

on-

sum

er

Pro

ducts

)

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Impact of Changes to Voluntary Standards for Gas Space Heaters* and Gas Furnaces: A Comparison

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 1994Source: 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

1 20

200

400

600

800

1000

1200

535

1024

230 199

1982-1990 (Before) 1999-2007 (After)

9-Year period of estimate

Tota

l Ann

ual C

O D

eath

s As

socia

ted

with

Gas

Fur

nace

s an

d Sp

ace

Heat

ers a

nd P

orta

ble

Gas H

eate

rs

Gas Furnaces Gas Space Heaters

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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.

CPSC Staff’s CO Shutoff Proposal

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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)

Sensor Testing Conducted by CPSC to Support the CO Shutoff Proposal

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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).

Actions Taken by ANSI Z21/83 Technical Committee

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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)

Sensor Testing Conducted by CPSCto Examine ANSI Z21/83 Concerns

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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

International Standards Development Organizations (SDOs)

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Panel Session II:Industry Presentations

Carbon Monoxide/Combustion Sensor Forum