High Levels Of Carbon Monoxide Research Articles

Exposures to High Levels of Carbon Monoxide from Wood-fired Temazcal (Steam Bath) Use in Highland Guatemala

Exposures to High Levels of Carbon Monoxide from Wood-fired Temazcal (Steam Bath) Use in Highland Guatemala

Exposures to High Levels of Carbon Monoxide from Wood-fired Temazcal (Steam Bath) Use in Highland Guatemala

The temazcal is a wood-fired steam bath used in the rural highlands of Guatemala for bathing and healing. We measured carbon monoxide (CO) among 288 participants in 72 temazcales. Participants were drawn from communities who participated in the RESPIRE (Randomized Exposure Study of Pollution Indoors and Respiratory Effects) chimney stove intervention trial. Temazcal CO exposures were extremely high, averaging 431 parts per million (time-weighted average). Compared to kitchen wood-smoke exposures, the temazcal contributes significantly to weekly exposures, despite the fact that the population spends less time in the temazcal than in the kitchen. This report 1) describes temazcal use patterns; 2) reports participants' signs and symptoms during temazcal use; 3) models the distribution of temazcal CO concentrations; 4) assesses reliability of exhaled breath CO as a biomarker of CO exposure; and 5) provides a proportional analysis of CO concentrations from temazcal use, as compared to kitchen concentrations.

Carbon Monoxide Levels Among Patrons of Hookah Cafes

Individuals who use a hookah (water pipe) as a method of tobacco smoking are exposed to high levels of carbon monoxide (CO). Assessing hookah use in one of the venues of its use (hookah bars) will aid the understanding of the toxins and exposure for the user. In Florida, smoking is prohibited in public places under the Florida Clean Indoor Act but permitted in establishments that have less than 10% gross revenue from food. To assess the CO level of hookah cafe patrons, using traditional bar patrons as a comparison. After IRB approval, a nighttime field study of patrons (aged >18 years) exiting hookah cafes and traditional bars in 2009 was conducted, using sidewalk locations immediately outside these establishments in a campus community. As hookah cafes and bars are typically entered and exited in groups, every other group of people exiting the establishment was approached. For comparison purposes, the sample collected was similar in number, 173 hookah cafe and 198 traditional bar participants. Results from analysis conducted in 2010 indicate that patrons of hookah cafes had significantly higher CO levels (mean=30.8 parts per million [ppm]) compared to patrons of traditional bars (mean=8.9 ppm). Respondents who indicate no cigarette use in the past month but had visited a hookah cafe still demonstrated significantly higher CO values (mean=28.5 ppm) compared to those exiting traditional bars (mean=8.0 ppm). Current cigarette smokers also produced significantly more CO if exiting a hookah cafe (mean=34.7 ppm) compared to a traditional bar (mean=13.3 ppm). CO levels are higher for patrons of hookah cafes, for both current and non-cigarette smokers. Although users report that they perceive hookah to be less harmful than cigarettes, the greater CO exposure for hookah users that was observed in this study is not consistent with that perception.

Validation of the respiratory toxics exposure score (RTES) for chronic obstructive pulmonary disease screening

Our aim is to evaluate the validity of exhaled carbon monoxide (CO) and of a newly-created score as markers of Chronic Obstructive Pulmonary Disease (COPD). The CO level was measured in a derivation subsample of a cross-sectional study and linked to COPD diagnosis; its predictors were evaluated, and a scale was constructed. It was evaluated in a validation subsample and in a clinical setting. Individuals with COPD had higher CO levels than healthy individuals. CO level significant predictors were cigarettes per day, waterpipes per week, lower age, male gender, living close to diesel exhaust, heating home with the use of diesel, and having indoor family smokers. A score composed of CO predictors was able to significantly predict COPD (Ora = 4-7.5). Coupled with the clinical judgment of physicians, this scale would be an excellent low-cost tool for screening COPD, in absence of spirometry.

Observations of carbon monoxide mixing ratios at a mountain site in central Taiwan during the Asian biomass burning season

Carbon monoxide (CO) mixing ratios were observed from 30 January to 7 April 2008 at Mt. Lulin (23.51°N, 120.92°E, 2862 m asl) in central Taiwan to investigate characteristics of CO during biomass burning periods. During the sampling campaign, the average mixing ratio of CO was 234 ± 63 ppb with higher levels observed in March. The elevated CO in March can, on the basis of backward trajectories and satellite fire spots analyses, possibly be attributed to biomass burning activities in the Asian continent. Significant diurnal variations of CO mixing ratios were observed at the remote site. The higher CO levels in the afternoon were influenced by the transport of boundary layer pollution to the site during daytime upslope flow. Backward trajectory analysis showed that air masses mainly originated from India (ID), the Indochina Peninsula (IP) and South Coastal China (SC), which together accounted for 85% of the total trajectories. Higher mixing ratios of CO were found in the ID, IP, and SC categories, indicating significant impacts of anthropogenic emissions on the Pacific region. Furthermore, the air parcels were divided into two categories, those that passed over the fire regions and those that did not. The result showed that the average difference of CO levels between the two categories was approximately 79 ppb, suggesting that Asian biomass burning plays an important role in CO levels at this remote site during the springtime.

Beneficial effects of the heme oxygenase-1/carbon monoxide system in patients with severe sepsis/septic shock

We evaluated the relations among the arterial carbon monoxide (CO) concentration, heme oxygenase (HO)-1 expression by monocytes, oxidative stress, plasma levels of cytokines and bilirubin, and the outcome of patients with severe sepsis or septic shock. Thirty-six patients who fulfilled the criteria for severe sepsis or septic shock and 21 other patients without sepsis during their stay in the intensive care unit were studied. HO-1 protein expression by monocytes, arterial CO, oxidative stress, bilirubin, and cytokines were measured. Arterial blood CO, cytokine, and bilirubin levels, and monocyte HO-1 protein expression were higher in patients with severe sepsis/septic shock than in non-septic patients. Increased HO-1 expression was related to the arterial CO concentration and oxidative stress. There was a positive correlation between survival and increased HO-1 protein expression or a higher CO level. Arterial CO and monocyte HO-1 protein expression were increased in critically ill patients, particularly those with severe sepsis or septic shock, suggesting that oxidative stress is closely related to HO-1 expression. The HO-1/CO system may play an important role in sepsis.

Spatial Heterogeneity in Environmental Regulation Enforcement and the Firm Location Decision among U.S. Counties

We estimate a negative binomial model with fixed effects to examine the impact of spatial differences in environmental regulation on manufacturing capital flows. Using a newly available data set, we find that stricter air quality standards with respect to ozone deter births of polluting plants, suggesting that heterogeneity in regulatory standards may create a spatial browning process. We also find that spatial differences in environmental regulation do not play a role in the location decision of plants that are not pollution-intensive. Finally, we also examine the effects on capital flows with respect to three other criteria air pollutants regulated under the amendments to the Clean Air Act. We find that births of particulates-intensive manufacturers are deterred by stricter regulation with respect to particulates emissions but the location decisions of plants that emit high levels of carbon monoxide and sulfur dioxide are not significantly affected by increased regulation of the respective criteria pollutant.

Comparison of subjective, pharmacokinetic, and physiological effects of marijuana smoked as joints and blunts

Recent increases in marijuana smoking among the young adult population have been accompanied by the popularization of smoking marijuana as blunts instead of as joints. Blunts consist of marijuana wrapped in tobacco leaves, whereas joints consist of marijuana wrapped in cigarette paper. To date, the effects of marijuana smoked as joints and blunts have not been systematically compared. The current within-subject, randomized, double-blind, placebo-controlled study sought to directly compare the subjective, physiological, and pharmacokinetic effects of marijuana smoked by these two methods. Marijuana blunt smokers (12 women and 12 men) were recruited and participated in a 6-session outpatient study. Participants were blindfolded and smoked three puffs from either a blunt or a joint containing marijuana with varying Δ 9-tetrahydrocannabinol (THC) concentrations (0.0, 1.8, and 3.6%). Subjective, physiological (heart rate, blood pressure, and carbon monoxide levels) and pharmacokinetic effects (plasma THC concentration) were monitored before and at specified time points for 3 h after smoking. Joints produced greater increases in plasma THC and subjective ratings of marijuana intoxication, strength, and quality compared to blunts, and these effects were more pronounced in women compared to men. However, blunts produced equivalent increases in heart rate and higher carbon monoxide levels than joints, despite producing lower levels of plasma THC. These findings demonstrate that smoking marijuana in a tobacco leaf may increase the risks of marijuana use by enhancing carbon monoxide exposure and increasing heart rate compared to joints.

Entertainment‐education and CO poisonings in ciudad Juárez: A case study of El Asesino invisible*

Residents in peri‐urban, low‐income colonias from Ciudad Juárez, México, are at high risk for carbon monoxide (CO) intoxication from the use of unvented, indoor heaters. To address this risk, a comic book‐style communication protocol was developed using the mental models approach and the entertainment‐education (EE) communication strategy to help colonia residents properly use this home heating method. El Asesino Invisible (The Invisible Assassin) encouraged people to buy a CO alarm for the home and provided information about CO intoxication. Part of a larger research agenda, the health campaign data were gathered from residents in colonias where high levels of indoor CO were previously measured. The essay provides an overview of the EE process and related strategies for reaching low‐income, colonia audiences. Limitations are addressed and ideas for future research are provided.

Acute carbon monoxide poisoning with severe cardiopulmonary compromise: a case report

IntroductionCarbon monoxide (CO) is a colorless, odorless gas produced as a by-product of incomplete combustion, and a common source is the fuel used for heating water in homes. The clinical presentation of CO poisoning may be mild, moderate, or severe.Case presentationThis paper describes carbon monoxide (CO) poisoning in a 15-year-old child who suffered from severe cardiopulmonary compromise without overt neuropsychiatric sequelae. This occurred after he was exposed to a home heater producing high levels of carbon monoxide for an estimated six to eight hours. CO-induced cardiopulmonary compromise is infrequent in children.ConclusionIn this case, prolonged exposure to CO resulted in a high carboxyhemoglobin (COHb) concentration, but the child recovered without overt sequelae, despite severe cardiopulmonary compromise.

Atmospheric Emissions from a Passenger Ferry with Selective Catalytic Reduction

The two main propulsion engines on Staten Island Ferry Alice Austen (Caterpillar 3516A, 1550 hp each) were fitted with selective catalytic reduction (SCR) aftertreatment technology to reduce emissions of oxides of nitrogen (NOx). After the installation of the SCR system, emissions from the ferry were characterized both pre- and post-aftertreatment. Prior research has shown that the ferry operates in four modes, namely idle, acceleration, cruise, and maneuvering modes. Emissions were measured for both engines (designated NY and SI) and for travel in both directions between Manhattan and Staten Island. The emissions characterization used an analyzer system, a data logger, and a filter-based particulate matter (PM) measurement system. The measurement of NOx, carbon monoxide (CO), and carbon dioxide (CO2) were based on federal reference methods. With the existing control strategy for the SCR urea injection, the SCR provided approximately 64% reduction of NOx for engine NY and 36% reduction for engine SI for a complete round trip with less than 6.5 parts per million by volume (ppmv) of ammonia slip during urea injection. Average reductions during the cruise mode were 75% for engine NY and 47% for engine SI, which was operating differently than engine NY. Reductions for the cruise mode during urea injection typically exceeded 94% from both engines, but urea was injected only when the catalyst temperature reached a 300 °C threshold pre- and postcatalyst. Data analysis showed a total NOx mass emission split with 80% produced during cruise, and the remaining 20% spread across idle, acceleration, and maneuvering. Examination of continuous NOx data showed that higher reductions of NOx could be achieved on both engines by initiating the urea injection at an earlier point (lower exhaust temperature) in the acceleration and cruise modes of operation. The oxidation catalyst reduced the CO production 94% for engine NY and 82% for engine SI, although the high CO levels during acceleration did cause analyzers to over-range. No clear, quantitative conclusions could be made regarding the effects of the SCR on PM

A chemical kinetic study of n-butanol oxidation at elevated pressure in a jet stirred reactor

Biofuels are attractive alternatives to petroleum derived transportation fuels. n-Butanol, or biobutanol, is one alternative biofuel that can replace gasoline and diesel in transportation applications. Similar to ethanol, n-butanol can be produced via the fermentation of sugars, starches, and lignocelluloses obtained from agricultural feedstocks. n-Butanol has several advantages over ethanol, but the detailed combustion characteristics are not well understood. This paper studies the oxidation of n-butanol in a jet stirred reactor at 10atm and a range of equivalence ratios. The profiles for CO, CO2, H2O, H2, C1–C4 hydrocarbons, and C1–C4 oxygenated compounds are presented herein. High levels of carbon monoxide, carbon dioxide, water, hydrogen, methane, formaldehyde, ethylene, and propene are detected. The experimental data are used to validate a novel detailed chemical kinetic mechanism for n-butanol oxidation. The proposed mechanism well predicts the concentration of major product species at all temperatures and equivalence ratios studied. Insights into the prediction of other species are presented herein. The proposed mechanism indicates that n-butanol consumption is dominated by H-atom abstraction from the α, β, and γ carbon atoms. A sensitivity analysis is also presented to show the effects of reaction kinetics on the concentration of several poorly predicted species.

Hazardous Off-Gassing of Carbon Monoxide and Oxygen Depletion during Ocean Transportation of Wood Pellets

Five ocean vessels were investigated for the characterization and quantification of gaseous compounds emitted during ocean transportation of wood pellets in closed cargo hatches from Canada to Sweden. The study was initiated after a fatal accident with several injured during discharge in Sweden. The objective with the investigation was to better understand the off-gassing and issues related to workers' exposure. Air sampling was done during transport and immediately before discharge in the undisturbed headspace air above the wood pellets and in the staircase adjacent to each hatch. The samples were analyzed with Fourier transform infrared spectroscopy and direct reading instruments. The following compounds and ranges were detected in samples from the five ships: carbon monoxide (CO) 1460–14650 ppm, carbon dioxide (CO2) 2960–21570 ppm, methane 79.9–956 ppm, butane equivalents 63–842 ppm, ethylene 2–21.2 ppm, propylene 5.3–36 ppm, ethane 0–25 ppm and aldehydes 2.3–35 ppm. The oxygen levels were between 0.8 and 16.9%. The concentrations in the staircases were almost as high as in the cargo hatches, indicating a fairly free passage of air between the two spaces. A potentially dangerous atmosphere was reached within a week from loading. The conclusions are that ocean transportation of wood pellets in confined spaces may produce an oxygen deficient atmosphere and lethal levels of CO which may leak into adjacent access spaces. The dangerous combination of extremely high levels of CO and reduced oxygen produces a fast-acting toxic combination. Measurement of CO in combination with oxygen is essential prior to entry in spaces having air communication with cargo hatches of wood pellets. Forced ventilation of staircases prior to entry is necessary. Redesign, locking and labeling of access doors and the establishment of rigorous entry procedures and training of onboard crew as well as personnel boarding ocean vessels are also important.

The Role of Environmental Factors in the Causation of Sudden Death in Infants: Two Cases of Sudden Unexpected Death in Two Unrelated Infants Who Were Cared for by the Same Babysitter

We report two cases of sudden unexpected death in two unrelated African American female infants, 2 months and 4 months old. Both infants were attended to by the same babysitter in the same apartment and died 39 days apart in the same bed and in the same bedroom. The autopsy of the first infant revealed sudden unexplained death in an infant. Toxicologic analysis for carbon monoxide (CO) was not performed because it was not suspected. When the second infant died, investigation into the ambient air quality within the apartment revealed high levels of CO emanating from a poorly ventilated and defective hot water heater, which was located across a hallway from the bedroom where the two babies died. CO saturation levels in the postmortem blood samples of the two babies were elevated and were similar (13% and 14%). Nicotine and cotinine were not detected in the blood sample of the two infants. Cherry-red livor mortis was absent. Acute CO intoxication was determined to be the underlying cause of these two unexpected deaths. These two cases underscore the need to integrate ambient air analysis and postmortem CO analysis as routine components of the comprehensive death investigation of infants who die suddenly and unexpectedly.

Modelling constraints on the emission inventory and on vertical dispersion for CO and SO<sub>2</sub> in the Mexico City Metropolitan Area using Solar FTIR and zenith sky UV spectroscopy

Abstract. Emissions of air pollutants in and around urban areas lead to negative health impacts on the population. To estimate these impacts, it is important to know the sources and transport mechanisms of the pollutants accurately. Mexico City has a large urban fleet in a topographically constrained basin leading to high levels of carbon monoxide (CO). Large point sources of sulfur dioxide (SO2) surrounding the basin lead to episodes with high concentrations. An Eulerian grid model (CAMx) and a particle trajectory model (FLEXPART) are used to evaluate the estimates of CO and SO2 in the current emission inventory using mesoscale meteorological simulations from MM5. Vertical column measurements of CO are used to constrain the total amount of emitted CO in the model and to identify the most appropriate vertical dispersion scheme. Zenith sky UV spectroscopy is used to estimate the emissions of SO2 from a large power plant and the Popocatépetl volcano. Results suggest that the models are able to identify correctly large point sources and that both the power plant and the volcano impact the MCMA. Modelled concentrations of CO based on the current emission inventory match observations suggesting that the current total emissions estimate is correct. Possible adjustments to the spatial and temporal distribution can be inferred from model results. Accurate source and dispersion modelling provides feedback for development of the emission inventory, verification of transport processes in air quality models and guidance for policy decisions.

Carbon monoxide levels along roadway

This paper predicts and compares the carbon monoxide (CO) concentration levels along Sembulan Road for years 2004 and 2014 using CAL3QHC air dispersion model at two major locations, i.e., at Sembulan Roundabout and Sutera Harbour Intersection, Kota Kinabalu, Sabah, Malaysia. The CO concentration “hot-spots” were also identified at Sutera Harbour Intersection, and the highest maximum 1-hr average ground level concentrations of CO modeled for Kpg. Air Sembulan located in the northeast of idling road was 9.33 ppm for year 2004. This study showed that there would be no extreme changes in CO concentration trends for year 2014 although a substantial increase in the number of vehicles is assumed to affect the level of CO concentrations. It was also found that the CO levels would be well below the Malaysian Ambient Air Quality Guidelines of 30 ppm for 1-hour Time-Weighted Average (TWA). Comparisons between the modeled and observed outputs using quantitative data analysis technique and statistical methods indicated that the CAL3QHC predicted results correlated well with measured data. It was predicted that receptors located near to the major intersection, in the long-term would be potentially exposed to relatively higher CO levels.

The Impact of Local Air Quality on the Number of Hospital Admissions with Acute Pain in Sickle Cell Disease within an Urban Environment.

The clinical severity of sickle cell disease (SCD) is dependent on genetic and environmental variables. The impact of environmental factors on disease is a major public health issue and air pollution has been consistently correlated with poor health outcomes. Environmental factors in SCD have been poorly studied. We have retrospectively studied the numbers of daily admissions with vaso-occlusive sickle cell pain to King's College Hospital, London, in relation to local daily air quality measurements. We analysed 1047 patient episodes over 1400 days (1st January 1998 to 31st October 2001). Statistical time series analysis was performed using cross-correlation function (CCF), where the observations of one series are correlated with the observations of another series at various lags and leads, values >0.05 being significant. This showed a significant association between increased numbers of admissions and low levels of nitric oxide (NO) (CCF=0.063), low levels of carbon monoxide (CO) (CCF=0.064) and high levels of ozone (O3) (CCF=0.067). There was no association with sulphur dioxide (SO2), nitric dioxide (NO2) or dust. The significant results were further examined using quartile analysis. This confirmed that increased numbers of hospital admissions were associated with high levels of O3 (oneway ANOVA p=0.039) and low levels of CO (oneway ANOVA p=0.042). Low NO levels were also associated with increased admissions, not however reaching statistical significance on quartile analysis (oneway ANOVA p=0.158). O3 levels show marked seasonal variation, with high levels occurring in summer months in the UK. We have previously shown a trend towards increased admissions in the summer months with acute sickle related pain, whereas other groups, which are primarily based in rural tropical climates, found increased admissions in cold, rainy months. The adverse effect of high O3 levels may explain this difference. There is no direct evidence to explain the mechanism by which high O3 levels leads to vaso-occlusion in SCD but high levels of O3 have been linked to reduced respiratory function, which may in turn precipitate vaso-occlusion. Independent studies have shown high CO levels are linked to increased respiratory and cardiovascular admissions. Paradoxically we found that high CO levels were linked to decreased admission numbers and may be protective against acute pain in SCD. CO may confer benefit by forming carboxyhaemoglobin that cannot polymerise resulting in decreased sickling. Previous studies have shown prolonged red cell survival in vivo following administration of CO to patients with SCD. Our study also suggests higher levels of atmospheric NO are linked to fewer admissions. NO is known to be central in the pathophysiology of vaso-occlusion and sickle cell patients are thought to have functional deficiency of NO. Many groups have reported inhaled NO as beneficial in the treatment of sickle pain. Our study suggests air quality has a significant effect on acute pain in SCD and that patients should be counselled accordingly. Based on these findings it would be appropriate to warn patients that high O3 levels might precipitate complications of SCD. The potential beneficial effect of CO and NO is intriguing and requires further investigation.

Transient carbon monoxide inhibits the ventilatory responses to hypoxia through peripheral mechanisms in the rat

Hypoxia inhibits K + channels of chemoreceptors of the carotid body (CB), which is reversed by transient carbon monoxide (CO), suggesting an inhibitory effect of CO on hypoxic stimulation of carotid chemoreceptors. Therefore, we hypothesized that the ventilatory responses to hypoxic stimulation of the CB might be depressed in intact rats by transient inhalation of CO. Anesthetized, spontaneously breathing rats were exposed to room air, and 1 min of 11% O 2 (HYP) and CO (0.25–2%) alone and in combination (HYP + CO). We found that transient CO did not affect baseline cardiorespiratory variables, but significantly attenuated hypoxic ventilatory augmentation, predominantly via reduction of tidal volume. To distinguish whether this CO modulation occurs at the CB or within the central nervous system, the cardiorespiratory responses to electrical stimulation of the fastigial nucleus (FN), a cerebellar nucleus known excitatory to respiration, were compared before and during transient CO. Our results showed that the FN-mediated cardiorespiratory responses were not significantly changed by transient CO exposure. To evaluate the effect of CO accumulation, we also compared baseline cardiorespiratory responses to 5 min of 1% and 2% CO, respectively. Interestingly, only the latter produced a biphasic ventilatory response (initial increase followed by decrease) associated with hypotension. We conclude that eupneic breathing in anesthetized rat was not affected by transient CO, but was altered by prolonged exposure to higher levels of CO. Moreover, transient CO depresses hypoxic ventilatory responses mainly through peripherally inhibiting hypoxic stimulation of carotid chemoreceptors.

Observational study of ozone and carbon monoxide at the summit of mount Tai (1534m a.s.l.) in central-eastern China

We report measurement results of ozone (O3) and carbon monoxide (CO) obtained from 5 Julyto 23 November 2003 at the summit of Mount Tai (1534 m a.s.l, 36.251N, 117.101E) in the Shandong Peninsula of China. The studywas carried out to gain insights into regional O3 pollution and air-mass transport in the highlypopulated North China (Huabei) Plains. The average mixing ratio was 58 (716) ppbv for O3 and 393 (7223) ppbv for CO during the studyperiod. The monthlyvariations in O 3 and CO exhibited a similar pattern, i.e. high in summer and low in autumn. While such a seasonal pattern for O3 is a common phenomenon in manyrural areas in the Northern Hemisphere and is mainlydue to seasonal changes in solar radiation and temperature, the higher CO levels in summer were attributed to the difference in dynamic transport and the evolution of PBL heights in summer and autumn over this region. An examination of diurnal variations in O3 indicated evident daytime photochemical production, especially in summer. The evolution of PBL heights and mountain-valleybreezes also had a large impact on the diurnal patterns of O 3 and CO. O3 and CO showed a moderatelygood positive correlation ( r ¼ 0:60) in Julywith a slope of 0.08 ppbv/ppbv, which is much lower than the slope (0.3–0.4 ppbv/ppbv) observed in North America. A back trajectoryanaly sis showed that air masses mainlyoriginated from the North China Plains or were re-circulating over the Shandong Peninsula, collectivelyaccounting for 76% of the air masses sampled. Summertime air traveling in the lower troposphere over northern China had the highest concentrations of O3 and CO, revealing that the lower troposphere in northern China was significantlypolluted in summer due to strong convection transporting PBL pollution to the free troposphere. The trajectories also showed notable contributions from eastern China, central China, and countries in northeast Asia such as Korea and Japan. r 2005 Published byElsevier Ltd.

A report of dangerously high carbon monoxide levels within the passenger compartment of a snow-obstructed vehicle.

BackgroundWe sought to determine how quickly carbon monoxide would accumulate in the passenger compartment of a snow-obstructed vehicle.MethodsA 1992 sedan was buried in snow to the level of the undercarriage, the ignition was then engaged and carbon monoxide levels recorded at 2.5-minute intervals. The primary outcome was the time at which a lethal carbon monoxide level was detected. Six trials were conducted: windows closed; windows open one inch; windows open 6 inches; windows closed and tailpipe swept clear of snow; windows closed and one cubic foot of snow removed around tailpipe; windows closed and tailpipe completely cleared of snow to ground level in a path 12 inches wide.ResultsLethal levels of carbon monoxide occurred within 2.5 minutes in the vehicle when the windows were closed, within 5 minutes when the widows were opened one inch, and within 7.5 minutes when the widows were opened six inches. Dangerously high levels of carbon monoxide were detected within the vehicle when the tailpipe had been swept clear of snow and when a one cubic foot area had been cleared around the tailpipe. When the tailpipe was completely unobstructed the carbon monoxide level was zero.ConclusionsLethal levels of carbon monoxide occurred within minutes in this snow-obstructed vehicle.