Carbon Monoxide in the Home A Community Workshop Presented by William W. Hill, Ph.D. Department of Urban Planning Ball State University Sponsored by the Community Outreach Partnership Center and East Central Reinvestment Corporation Improving the performance of our homes through the application of building science It s not rocket science. But it is science December 3, 2002 Part I Health effects of CO Production of CO Symptoms How it works in the body Recent medical findings Long-term effect of acute exposure Effects of chronic exposure Part II Sources of CO in the home Really bad ideas Garages Fireplaces Furnaces Ovens Water heaters Single return systems CO -- the senseless killer Colorless, odorless, tasteless and deadly U.S. data Leading cause of poisoning deaths, with an estimated 40,000 ER visits per year 450 unintentional deaths per year in U.S. CO poisoning from fuel-burning appliances in the home kills more than 200 people each year and sends about 10,000 to emergency rooms Statistics are probably seriously under-reported because CO poisoning is often misdiagnosed An excellent CO web site: coheadquarters.com Created and maintained by: David G. Penney, Ph.D. Professor of Physiology and Adjunct Professor of Occupational and Environmental Health Wayne State University, Detroit, MI William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 1
Deaths (unintentional) per 1,000 from CO CO is produced by incomplete combustion CO poisoning symptoms Early symptoms mimic the flu -- headaches, fatigue, nausea, dizzy spells, confusion, irritability CO reduces oxygen delivery to the brain, resulting in failure to think clearly, failure to recognize the warning signs Higher levels of CO result in loss of consciousness and death CO myths and misconceptions A blue flame produces no CO CO poisoning indicated by cherry red skin coloring CO poisoning can be checked by EMT with a pulse oximeter CO in the body When inhaled, CO bonds with hemoglobin, displacing oxygen and forming carboxyhemoglobin (COHb) Results in lack of O 2 supply to cells Attraction between CO and hemoglobin is about 250 times stronger than attraction between O 2 and hemoglobin CO dose is function of CO concentration times length of exposure William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 2
Effect = function of CO concentration times duration of exposure 200 ppm for 2-3 hours 400 ppm for 1-2 hrs 800 ppm for 45 minutes 1600 ppm for 20 minutes 3200 ppm for 5-10 min. Mild headache; fatigue, nausea, dizziness Serious headache, other symptoms intensify Dizziness, nausea, convulsions, unconscious within 2 hours Death within 1 hour Death within 1 hour Other factors which affect CO s impact Person s age and sex Activity level (physical exertion => increases respiration => increases CO uptake Overall health At risk populations The unborn are very susceptible CO is probably a cause here William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 3
Children also are at greater risk CO and gender issues Higher metabolic rates (i.e, use oxygen faster) Higher O 2 requirements Less able to fully explain onset, progression and severity of symptoms Young children spend most of their time in the home Why are women at higher risk? Why are they more apt to be misdiagnosed? Removal of CO from body is slow Emerging medical evidence of CO effects in two areas Long-term impacts of acute exposure Effects of chronic exposure Long-term impacts of acute exposure Previous belief: If you made it out to the fresh air, you survived and fully recovered Now we know the long-term effects can be debilitating Up to 40% of survivors of acute CO poisoning have memory impairment and other permanent health problems Prognosis for recovery worse than stroke or concussion -- David Penney Chronic CO exposure Exposure to low level CO concentrations over many days Just beginning to be recognized Looks a lot like MCS (multiple chemical sensitivity) May well have same etiology as MCS CO has a function in brain chemistry William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 4
Some CO history Illuminating gas used in homes in the 1800s had a high CO content It wasn t natural gas, but manufactured gas: Coal gas created as byproduct of coke mfg. Water gas created by spraying water over white-hot hard coal or coke Use of these gases probably resulted in high CO concentrations in the homes of the well-to-do Edgar Allen Poe, CO poster child Albert Donnay s research on symptoms consistent with CO poisoning in the stories of Edgar Allen Poe 30 symptoms taken from Poe s writings in The Fall of the House of Usher This list given to persons with chronic CO poisoning and a control group of healthy individuals Some symptoms from Poe s The Fall of the House of Usher a morbid acuteness of the senses insipid food was alone endurable the odors of all flowers were oppressive eyes were tortured by even a faint light phantasmagoric conceptions wild fantasies overpowered by an intense sentiment of horror, unaccountable yet unendurable Results of Donnay s research Respondents were asked to check those symptoms which they had experienced in the last two months Persons with chronic CO poisoning checked 27 of 30 symptoms Healthy control group checked 2 symptoms And have I not told you that what you mistake for madness is but overacuteness of the senses? Edgar Allen Poe, The Tell-Tale Heart William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 5
Allowable levels of CO 9 ppm -- EPA s ambient air quality standard, 8- hour average limit for exposure outdoors 11 ppm -- Health Canada s 8-hour average legal limit 35 ppm -- EPA s ambient air quality standard 1- hour average limit 50 ppm -- OSHA s 8-hour average legal limit for occupational CO exposure (highest occupational CO limit in the world!) CO Alarms You can t afford not to have one in your home Should be required, same as smoke alarms However, there is concern that they don t provide as much protection as they should CO home detector alarm requirements, first set by UL and CPSC in 1992, have been relaxed twice since Relaxed first in October 95, following Chicago false alarms caused by outdoor pollution trapped by inversion Relaxed again in October 98 UL/CPSC Standards for CO Alarms 1992 UL 2034 1998 UL 2034 CO Time until CO Time until Minimum time (ppm) alarm sounds (ppm) alarm sounds before alarm 15 8 hrs 15 30 days -- 100 90 minutes 70 189 minutes 60 200 35 minutes 150 50 minutes 10 400 15 minutes 400 15 minutes 4 Current detector lower limits Rationale of current standards 30 ppm -- lowest level that CO detectors may display 70 ppm -- lowest level at which CO detectors may alarm More sensitive detectors are available with a doctor s prescription Designed to protect against acute CO poisoning Designed to protect average, healthy adults Not designed to protect against chronic low level exposure William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 6
Permissible Exposure Levels (PELs) for industrial workplaces have increased OSHA old 8-hour PEL was 35 ppm OSHA s new 8-hour PEL is 50 ppm While CO alarm thresholds and PELs have gone up, TLVs have gone down Threshold Limit Values (TLVs) are set by the American Conference of Government Industrial Hygienists These continue to go lower as more information becomes available 1946-1966 TLV = 100 ppm 1967 TLV = 50 ppm 1992 TLV = 25 ppm Some interesting maximum limits set by ANSI (American National Standards Institute) Allowed from unvented space heaters -- 200 ppm Allowed in furnace flue gas -- 400 ppm Allowed for emissions from an unvented gas oven -- 800 ppm Note: All ppm limits above are for air-free measurements Part II -- CO in the home Review of Building Sciences fundamentals CO sources Orphaned water heaters Backdrafting water heaters Single return systems Attic fans Building Science Fundamentals Necessary but not sufficient conditions Source Hole Driving force Driving forces Wind Stack effect Furnaces fans (air handlers or blowers) Potential sources of CO in a home Automobile (in attached or tuck under garage Generator, lawn mower, other small engine in garage Charcoal grills Fireplace Water heater Oven/stove Unvented space heater Furnace/boiler Gas dryer William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 7
CO production Natural gas appliances, when operating correctly, produce very little CO Solid fuel combustion (wood fires, charcoal) produce CO all of the time Automobiles produce CO all of the time, but more when cold Small gas engines produce lots of CO Some really bad ideas! Dangerous! Charcoal grilling inside or in the garage Running a generator in the garage Running small engines in the garage Attached and tuck under garages The building science: Source of CO -- vehicle (or small engines) Hole -- holes between garage and house Driving force -- stack effect Solutions: Don t warm up car in garage Seal air leakage paths between house and garage Furnaces in garages can be dangerous Return system (plenum and ducts) needs to be airtight If not airtight, the return sucks air from garage into the home What might be in that air? CO Plus volatiles from all sorts of other hazardous materials that people store in the garage Furnaces & boilers Plugged or broken chimneys/vent systems are a major cause of CO Cracked heat exchangers probably not a major cause of CO in homes? Improper adjustment of combustion appliance can cause CO production Over firing Gas pressure too high Incorrect orifice Flame impingement Flame cooling William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 8
Gas ovens The more of these we test, the more nervous we become I would not put one in a small tight house Might the post Thanksgiving dinner drowsies be caused in part by CO? Conjecture at this point, but worth investigating Cooking the turkey, not overeating, may well be a factor in why you feel drowsy after dinner Ovens can produce high concentrations of CO Combustion process often inadvertently modified by aluminum foil or placement of baking pans Ovens are unvented combustion appliances, with range hoods that are ineffective or not used Ovens are often operated for many hours on Thanksgiving day Gas oven and range with unvented range hood The oven s chimney (vent system) runs through the oven Don t cover those slots in the bottom of the oven! William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 9
Safe gas oven operation Never use it to heat the home! Do not operate with oven door open Do not cover the vent holes on the bottom of the oven with foil Do not block air vent holes Operate the range hood whenever oven is on Note: Range hood must exhaust to the outside Gas-fired water heaters Conventional (draft hood equipped) water heaters can be quite susceptible to backdrafting When they backdraft they spill combustion products into the homes Backdrafting can cause a water heater to make CO Conventional, atmospheric draft water heater is recognized by the draft diverter/draft hood on top Backdrafting water heater Air, instead of going up the chimney, is coming down the chimney If water heater comes on, all the combustion products end up inside the home Most common cause of backdrafting is pressure differences caused by unbalanced forced air systems or exhaust appliances William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 10
Two things required to make a gas water heater deadly 1. Has to be backdrafting or spilling 2. Has to be producing CO Discoloration below draft diverter is evidence of spillage Black carbon deposits on top of the water heater indicate serious spillage and CO Causes of CO production in water heaters Plugged flues Dirty burners Misaligned burners (flame impingement which causes flame cooling) Improperly adjusted gas pressure But there s more... Backdrafting and CO production are not independent of each other A water heater operating absolutely perfectly, producing zero ppm of CO, can immediately start producing high concentrations of CO when backdrafted From zero ppm CO to thousands of ppm CO in seconds! Scary!! William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 11
How backdrafting can cause water heaters to start making CO Back drafting puts a pressure cap on the top of the water heater, restricting the air flowing up the flue Less air flow out the top means less air being drawn in at bottom of water heater Combustion process doesn t get enough oxygen and starts producing CO Orphaned water heaters Especially a problem in older homes Happens when you replace an old inefficient furnace with a high efficiency condensing furnace Condensing furnace vents through PVC pipe Water heater is left connected to old masonry furnace Orphaned water heaters, continued Water heater isn t big enough to heat up the chimney and create draft Water heater spills combustion products into the house Spilling water heater can easily make CO Solutions to orphaned water heaters Replace the water heater with either: A high-efficiency gas water heater, or An electric water heater Or, run a smaller vent system inside the existing chimney Probably OK: Direct vent water heater Better: Power vented water heater William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 12
Best: Sealed combustion (two pipe) water heater Safe but higher operating costs: Electric water heater CO detector false alarms Most are not false at all! CO detector is in fact working properly Dangerous levels of CO are present The first responders and heating contractors can not find the source of the CO because they haven t received the necessary training They haven t been trained to look at the house as a system The building envelope and furnace/ac equipment interact and affect each other Furnace/AC fan can cause significant roomto-room pressure differences Pressure differences can cause water heater to backdraft and make CO If house isn t set up exactly as it was before, it s difficult to find the problem Fundamentals of building science A source A hole A driving force The source is the water heater even though it doesn t make CO when tested William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 13
The hole is the draft diverter/draft hood on the water heater The driving force is the furnace air handler (AKA blower or fan) Typical squirrel cage blower on forced air furnace Air handlers in forced-air systems can cause large driving forces (pressure differences) Fundamentals: Air move from high pressure to low pressure If a fan/air handler blows 1000 cfm out of the supply registers it must also suck 1000 cfm from the return registers Balanced system There are supply and return registers in every room (except kitchen and baths) No room-to-room pressure differences Result: No problems (unless house is small and tight) William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 14
Single (or central) return system is an unbalanced system Supplies, but no returns in BRs Return is in the hall/common area When BR doors are closed, air can t get back to the return BRs become pressurized (positive pressure) Rest of house is under negative pressure Result: PROBLEMS Potential problems from an unbalanced forced-air system H&S: Depressurization of the combustion appliance zone (CAZ) can cause water heaters to backdraft and spill Durability: Moisture-laden air forced into walls Comfort: Home doesn t heat or cool properly Affordability: Home costs more to heat and cool Other causes of combustion appliance zone (CAZ) depressurization Leaky ducts Other exhaust ventilation Clothes dryers Cooktop exhausts and range hoods Attic fans Bath fans Have to test house under worse case conditions Typical worst case conditions (though it s not quite this simple): BR doors closed Air handler on Furnace not on All exhaust fans on Clothes dryer on Measured air pressures wrt to outside in an 1150 ft 2 home under worst case conditions: Air handler on BR doors closed Bath fan on? Clothes dryer on William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 15
Another false alarm that wasn t Supply leaks can also depressurize houses With the BR doors closed, the central part of the house is depressurized This causes the water heater to backdraft The water heater, when backdrafted, makes CO If the house is not set up this way, they ll never find the source of CO and the incident will be will be incorrectly labeled as a false alarm Returns often leak at the filter rack and the leak is exacerbated by a dirty filter Clothes dryers can easily depressurize the CAZ in small tight homes William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 16
Solutions to the water heater CO problem 1. Remove the source -- do not use naturally drafted gas water heaters 2. Remove the driving force 1. Removing the source: Instead of natural draft water heaters, use... Electric (off-peak electric DHW is an especially nice solution where available) For gas-fired DHW, use: Direct vent and power vent Sealed combustion (two pipe) 2. Removing the driving force Prevent room-to-room pressure differences: In new construction: Do not install single return systems In existing homes: Pressure relieve the bedrooms Isolate the water heater from the driving force by putting the water heater outside the pressure envelope Pressure relief approaches Door undercuts Louvered doors Through-the-wall grills High-low grills in wall Jump duct (over the top of a wall) Put the CAZ outside the home s pressure barrier Use an equipment room (CAZ) with locking exterior doors, preferable with access from outside only Bring combustion air into the room Room still needs to be insulated William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 17
Fireplaces can both cause backdrafting and be backdrafted Carbon Monoxide Fireplaces and single return systems a deadly combination! What if this home had a fireplace? Powered attic ventilators can backdraft water heaters These are large fans with high flow rates If there are unsealed air leaks between the attic and living space below, the fan depressurizes the house Attic fan ends up sucking air down the flue on the water heater Other reasons why attic fans are a bad idea A thermostatically controlled attic fan can be a serious liability in a house fire Attic fans are, at best, a band aid solution to problems better solved in other ways What to ask heating contractor before hiring them to check your heating system Will your technician have a digital CO detector (e.g., a Monoxor)? Will he or she measure worst case draft? Is he or she certified by the Building Performance Institute (BPI)? William W. Hill, Department of Urban Planning, Ball State University, Muncie, IN 47306 18