- Email: [email protected]
Carbon monoxide and COHb concentration in blood in various circumstances
Energy and Buildings 35 (2003) 903–907
Carbon monoxide and COHb concentration in blood in various circumstances Jurij Modic∗ Faculty of Mechanical Engineering, University of Ljubljana, Askerceva 6, Ljubljana 1000, Slovenia Received 28 November 2002; accepted 2 February 2003
Abstract On the basis of known medical experiments we find out the correlation between the concentration of carbon monoxide (CO) in inhaling air and the concentration of carboxihemoglobyne (COHb) in human blood. All internal combustion engines produce exhaust gases containing noxious compounds: carbon monoxide, nitrogen oxides (NOx ), carbon oxides (CxHy) and smoke. In a living room is important the smoke of cigarettes, smoke of furnaces, improper ventilation. In tunnel is most dangerous the carbon monoxide if it exceed an allowable level. In human blood the carbon monoxide causes increasing the concentration of carboxihemoglobyne and in this case the hypoxia of web. With help of mathematical model the concentrations of some dangerous substances at the end of tunnel were calculated. For this case a differential equation also was developed and it shows the correlation between concentration of carbon monoxide in the air and concentration of carboxihemoglobyne in the blood. The constructed mathematical model shows circumstances in the tunnel (velocity of air moving as effect of induction, concentration of noxious substances and criterial number). Also a corresponding computer program was developed, which makes possible a quick and simple calculations. All the results are proved by experiments. Finally the differential equation was done, which shows a temporal connection between both parameters as a function of tunnel characteristics. © 2003 Published by Elsevier Science B.V. Keywords: Indoor air quality; Tunnel; Ventilation; Imissions; Hypoxia; Risk factor
1. Introduction [7] Carbon monoxide (CO) is the leading cause of accidental poisoning deaths, according to the Journal of the American Medical Association (JAMA). Fifteen hundred people die annually due to accidental carbon monoxide exposure, and additional 10,000 seek medical attention. Carbon monoxide is a flammable, colorless, odorless, tasteless toxic gas produced during incomplete combustion of fuel—natural gas, oil, coal, wood, kerosene, etc. Carbon monoxide inhibits the blood’s capacity to carry oxygen. In out lungs, CO quickly passes into our bloodstream and attaches itself to hemoglobin (oxygen carrying pigment in red blood cells). Hemoglobin readily accepts carbon monoxide—even over the life giving oxygen atoms (as much as 200 times as readily as oxygen) forming a toxic compound known as carboxyhemoglobyne (COHb). By replacing oxygen with carbon monoxide in our blood, our bodies poison themselves by cutting off the needed oxygen to our organs and cells, causing various amounts of damage—depending on exposure. ∗ Tel.: +386-1-47-71-315; fax: +386-1-25-18-567. E-mail address: [email protected] (J. Modic).
0378-7788/03/$ – see front matter © 2003 Published by Elsevier Science B.V. doi:10.1016/S0378-7788(03)00022-7
Indoor air quality (IAQ) refers to the effect, good or bad, of the contents of the air inside a structure, on its occupants. Usually, temperature, humidity, and air velocity are considered “comfort” rather than indoor air quality issues. Unless they are extreme, they may make someone unhappy, but they would not make a person ill. Nevertheless, most IAQ professionals will take these factors into account in investigating air quality situations. Good IAQ is the quality of air which has no unwanted gases or particles in it at concentrations which will adversely affect someone. Poor IAQ occurs when gases or particles are present at an excessive concentration so as to affect the satisfaction or health of occupants. In the minor instances, poor IAQ may only be annoying to one person. At the extreme, it could be fatal to all of the occupants of a structure. No building is perfectly sealed and so the air inside ultimately originates outside. Air pollution present in the outdoor environment will therefore enter into the building as well. Generally, pollutants present in the outdoor environment are present at a somewhat lower concentration than outside (probably 10–90% in most cases). There are several reasons for this. Some pollutants are absorbed by materials in the building. Others deteriorate or react chemically and so disappear. Still others may be filtered out by the ventila-
904
J. Modic / Energy and Buildings 35 (2003) 903–907
tion system. Also as it takes some time for the outdoor air to enter in quantities, there may be a delay from the time a contaminant appears outdoors, to when it becomes a problem indoors. Smog from outdoors reaches its peak indoors some time after the outdoor peak. Outdoor contaminants may be present indoors at a sufficient concentration to affect the occupants. Examples are pollen and mould spores from outdoors causing hay fever and allergies indoors; and high smog levels affecting occupants inside a building. Incidentally, there is no such thing as a good smog day close to a major highway (expressway/freeway).
2. Carbon monoxide poisoning [2,8] Carbon monoxide can cause neurological problems in mature persons, and learning disabilities and developmental trouble in children and can lead to miscarriage or stillbirth for women exposed during pregnancy. Because children have faster metabolic rates than adults, they require more oxygen for vital organs such as the brain and the heart. Since carbon monoxide interferes with oxygen delivery, it can lead to damage to an infant’s developing nervous system. One reason for higher CO concentration in the room is the smokers (Table 1). The average “for loading” of COHb by smokers is about 5% (see Table 1). The main problem of CO concentration is in tunnels and garages. For many years in the United States a rule of thumb of 0.155 m3 /(s per lane m) has been applied as the ventilation requirement for road tunnels. The tests conducted at the Memorial Tunnel have shown that this value is, in fact, a reasonable first pass at an emergency ventilation rate for a road tunnel in the United States. In 1975, the EPA issued a supplement to its Guidelines for Review of Environmental Statements for Highway Projects that evolved into a design approach based on keeping a CO concentration of 125 ppm (143 mg/m3 ) or below for a maximum of 1 h exposure time for tunnels located at or below an altitude of 1000 m. In Table 1 COHb concentration relative to cigarette consumptiona Cigarettes Smokers— Non-smokers— Studies per day COHb COHb 3–4 >5 5–10 11–20 11–20 >20 >20 >20 10–40 >40 30–80
3.6 4.1 5.1 6.6 6.1 6.7 7.3 5.0 5.9 6.9 11.6
2.5 1.6 2.5 2.5 1.3 1.3 2.5 0.9 1.3 1.3 0.6
Pankow et al., 1976 [7] Effenberger et al., 1957 [7] Pankow et al., 1976 Pankow et al., 1976 Castledon and Cole, 1975 [7] Castledon and Cole, 1975 [7] Pankow et al., 1976 Butt et al., 1974 [7] Goldsmith, 1974 [7] Goldsmith, 1974 [7] Smith and Landau, 1978 [7]
Mean
–
1.66
–
a
From [9].
1988, the EPA revised its recommendations for maximum CO levels in tunnels located at or below an altitude of 1500 m to the following: • maximum 120 ppm (137 mg/m3 ) for 15 min exposure time; • maximum 65 ppm (74 mg/m3 ) for 30 min exposure time; • maximum 45 ppm (52 mg/m3 ) for 45 min exposure time; • maximum 35 ppm (40 mg/m3 ) for 60 min exposure time. These guidelines do not apply to tunnels in operation prior to the adoption date. Permanent International Association of Road Congresses (PIARC) recommendation is different. Allowable concentration of carbon monoxide is 100 ppm, for the other noxious materials are: • kCOmax = 100 ppm; • kNOx max = 25 ppm; • kSmax = 7 × 10−3 m−1 (idle, 9 × 10−3 m−1 ; dangerous, 12 × 10−3 m−1 ). Outdoor air standards and regulations such as those from the Occupational Safety and Health Standards (OSHA) and the American Conference of Governmental Industrial Hygienists (ACGIH) are discussed in the section on bus terminals. At higher elevations the CO emission of vehicles is greatly increased, and human tolerance to CO exposure is reduced. For tunnels above 1500 m, the engineer should consult with medical authorities to establish a proper design value for CO concentrations. Unless specified otherwise, the material in this article refers to tunnels an altitude to 1500 m. In cities, about two-thirds of the carbon monoxide emissions come from transportation sources, with the largest contribution coming from highway motor vehicles. In urban areas, the motor vehicle contribution to carbon monoxide pollution can exceed 90%. In 1992, carbon monoxide levels exceeded the federal air quality standard in 20 US cities, home to more than 14 million people, than their uncontrolled counterparts of the 1960s. As a result, ambient carbon monoxide levels have dropped, despite large increases in the number of vehicles on the road and the number of miles they travel. With continued increases in vehicle travel projected, however, carbon monoxide levels will begin to climb again unless even more effective emission controls are employed (Table 2).
3. Connection between CO and COHb in tunnel [1–3] Referring to [2], 727 experiments on the mortal victims of CO poison (autopsy) were realized. Superficial look on the results shows anarchy. So we must find out the connection between some parameters. The main relation between CO and COHb depends on time of exposition, human activity, and altitude. The temperature of environment in all 727 cases was practically equal. If we take in account all parameters, we can find out the correlation between results, which can
J. Modic / Energy and Buildings 35 (2003) 903–907
905
Table 2 Influence of CO concentration in air on COHb concentration in blood Concentration of CO in aira
Effects, inhalation times and symptoms developed
1–2 ppm (0.0001%) 2 ppm (0.0002%) Above 2 ppm 9 ppm 15–20 ppm
Might be normal, from cooking stoves, spillage, outdoor traffic Suggested maximum long-term allowable exposure (source: some IAQ professionals) Raises questions about why CO is elevated The maximum allowable concentration for short term exposure in a living area (source: ASHRAE) Impaired performance in time discrimination (COHb: 2.0); decrease in absolute exercise time (COHb: 2.5); shortened time to angina response (COHb: 1.9); vigilance decrement (COHb: 3.0) (source: World Health Organization 13 {WHO 13}) 21% increase in cardio respiratory complaints Earlier onset of exercise-induced angina (COHb 4.96%) (source: WHO 13) The maximum allowable concentration for continuous exposure in any 8 h period, according to federal law Significant decrease in oxygen reserve available to the myocardium (COHb 10%) Slight headache, tiredness, dizziness, nausea after 2–3 h, might be life-threatening after 3 h (source: Bacharach) Frontal headaches within 1–2 h; life-threatening after 3 h Dizziness, nausea and convulsions within 45 min; unconsciousness within 2 h, death within 2–3 h Headache, dizziness and nausea within 20 min; death within 30 min Headache, dizziness and nausea within 5–20 min; quickly impaired thinking; death within 30 min Headache, dizziness and nausea within 1–2 min; thinking impaired before response possible; death within 10–15 min Death within 1–3 min
27 ppm (0.0027%) 30 ppm (0.0030%) 35 ppm (0.0035%) 75 ppm (0.0075%) 200 ppm (0.02%) 400 ppm (0.04%) 800 ppm (0.08%) 1600 ppm (0.64%) 3200 ppm (0.32%) 6400 ppm (0.64%) 12800 ppm (1.28%) a
Carbon monoxide (CO) 10,000 parts per million (ppm) = 1% by volume.
be approximated with equation in Excel software [4]. log COHb = 0.858 log kCO + 0.63 log(wfH t) − 2.30 1013.25 − 22.87H −5.255 fH = 1013.25
(1) (2)
where COHb is the COHb concentration in blood (%); t the time of exposure (min); kCO the CO concentration in air (ppm); w the activity; w = 1 for resting, w = 1.69 for walking, w = 2.81 for easy work, w = 3.77 for hard work; fH the influence of altitude; H the altitude (km). We find out that the correlation in this case is: r 2 = 0.998. After two steps (antilogarithm and differentiation) from Eq. (1), we obtain: dCOHb 0.86 (wfH )0.63 (wfH t)−0.37 (3) = 0.032kCO dt Eq. (3) is possible to solve numerical way (Runge-Kutta), or with software [5].
Fig. 1. CO concentration in tunnel.
A fire in the tunnel can be simulated, in which case a specified heat flux is added in a limited section of the tunnel. The variation of temperature along the tunnel is calculated using a function that describes how the relation between the increase of temperature in the air the time since the start of the fire.
4. CO concentration in tunnel [1,6] 4.2. The results of calculation 4.1. Available computer program For calculations we used program IDA [6]. IDA Road Tunnel Ventilation calculates air pressure, air flow, temperature as well as CO and nitrogen oxides (NOx ) contents in complex tunnel networks. The calculations are performed for a network of tunnels with an arbitrary geometry. The user enters a geometrical description of the tunnels, i.e. height and cross-section area along the length of the tunnel. Other input data are atmospheric conditions, including wind pressure, at the entrances of the tunnels, the amount of traffic through the tunnels, the emission of pollution, and coefficients of friction.
As an example we took in account a tunnel 3200 m long, with unidirectional traffic, standard geometry (A = 56 m2 ), 1000 vehicles/h, 40% of trucks, various velocities of vehicles, altitude 300 m, normal meteorological circumstances. The result of calculation is on Fig. 1 and Table 3.
5. COHb concentration in blood From Table 1 we find out, that the basic concentration of COHb in a smoker’s blood is 5% (average). This is a “for loading”. Now we solve the differential Eq. (3) by computer
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J. Modic / Energy and Buildings 35 (2003) 903–907
Table 3 CO concentration in tunnel
v (m/s) CO (ppm)
20 km/h
30 km/h
40 km/h
50 km/h
60 km/h
70 km/h
80 km/h
90 km/h
1.45 70.70
2.30 33.60
3.20 19.80
4.00 12.80
4.80 9.50
5.60 7.10
6.40 5.60
7.10 4.60
Fig. 2. Concentration COHb (kCO , t, v), L = 3200 m, M = 1000 h−1 . Fig. 4. Concentration COHb (kCO , t), kCO = 500 ppm.
program on numerical way [5], and we take in account for loading of 5%. 5.3. The case of fire 5.1. Tunnel is 3200 m long The critical COHb concentration is 25–30% [1,2]. In this case we can see that the danger in this tunnel is rare. By velocity 20 km/h in 3200 m long tunnel the driving time is about 10 min. In this case the COHb concentration is 17%. If the time is 30 min, the COHb concentration is 25% that is the boundary level for danger. By higher velocities is the COHb concentration lower: 60 km/h → 4 min → COHb = 6% (Fig. 2). 5.2. CO concentration in tunnel is 100 ppm In this case the CO concentration is on the allowed level, the fans must be switched on. The critical time is 20 min. After 20 min the COHb concentration in blood is higher as 25% that is dangerous (Fig. 3).
The CO concentration in this case is 500 ppm at least. The problem is that also a lot of other gases are present, they are poisonous, and the visibility is low (Fig. 4). The critical time is about 5 min. In this time the COHb concentration is 25%.
6. Conclusion Concentration of carbon monoxide under level 100 ppm (0.01%) is not dangerous because the risk limit about 25% of carboxihemoglobyne appears in time longer as 20 min, except by persons with great “for loading”. Danger appear also by very high concentrations of carbon monoxide (in case of fire: 500 ppm) or if tunnel ventilation by long tunnel is out of order, but in tunnels shorter as 3000 m in normal use there are no problems.
References
Fig. 3. Concentration COHb (kCO , t), CO = 100 ppm.
[1] J. Modic, Velocity Field and Concentration of Dangerous Gases in Tunnel, Dissertation, Faculty of Mechanical Engineering, Ljubljana, July 1997. [2] B. Müller, Gerichtliche Medizin, Zweite Auflage, Teil 2, Toxikology, Springer, Berlin, 1975. [3] J.G. Zankl, Berechnungen der CO Aufname des menschlichen Blutes Mitteilungen des Institutes fˆur Verbrennungskraftmaschinen und Thermodynamik, Technische Universität Graz, Heft 32 (1981). [4] Software EXCEL 7.0 for Windows XP, Microsoft, 2001.
J. Modic / Energy and Buildings 35 (2003) 903–907 [5] Wolfram, Mathematica A System for Doing Mathematics by Computer, Wolfram Research, Addison-Wesley, New York, 1996. [6] IDA, Road Tunnel Ventilation and Fire Simulation Software, Sundbyberg, Sweden, 2000. [7] Internet, Data from Internet.
907
[8] J. Modic, Motor vehicles emission in tunnel and COHb concentration in blood, Journal of Slovenian Medical Association, Ljubljana (1998) 75–78. [9] K.K. Jain, Carbon Monoxide Poisoning, Warren H. Green Inc., St. Louis, MO, 1990.
Carbon monoxide and COHb concentration in blood in various circumstances Jurij Modic∗ Faculty of Mechanical Engineering, University of Ljubljana, Askerceva 6, Ljubljana 1000, Slovenia Received 28 November 2002; accepted 2 February 2003
Abstract On the basis of known medical experiments we find out the correlation between the concentration of carbon monoxide (CO) in inhaling air and the concentration of carboxihemoglobyne (COHb) in human blood. All internal combustion engines produce exhaust gases containing noxious compounds: carbon monoxide, nitrogen oxides (NOx ), carbon oxides (CxHy) and smoke. In a living room is important the smoke of cigarettes, smoke of furnaces, improper ventilation. In tunnel is most dangerous the carbon monoxide if it exceed an allowable level. In human blood the carbon monoxide causes increasing the concentration of carboxihemoglobyne and in this case the hypoxia of web. With help of mathematical model the concentrations of some dangerous substances at the end of tunnel were calculated. For this case a differential equation also was developed and it shows the correlation between concentration of carbon monoxide in the air and concentration of carboxihemoglobyne in the blood. The constructed mathematical model shows circumstances in the tunnel (velocity of air moving as effect of induction, concentration of noxious substances and criterial number). Also a corresponding computer program was developed, which makes possible a quick and simple calculations. All the results are proved by experiments. Finally the differential equation was done, which shows a temporal connection between both parameters as a function of tunnel characteristics. © 2003 Published by Elsevier Science B.V. Keywords: Indoor air quality; Tunnel; Ventilation; Imissions; Hypoxia; Risk factor
1. Introduction [7] Carbon monoxide (CO) is the leading cause of accidental poisoning deaths, according to the Journal of the American Medical Association (JAMA). Fifteen hundred people die annually due to accidental carbon monoxide exposure, and additional 10,000 seek medical attention. Carbon monoxide is a flammable, colorless, odorless, tasteless toxic gas produced during incomplete combustion of fuel—natural gas, oil, coal, wood, kerosene, etc. Carbon monoxide inhibits the blood’s capacity to carry oxygen. In out lungs, CO quickly passes into our bloodstream and attaches itself to hemoglobin (oxygen carrying pigment in red blood cells). Hemoglobin readily accepts carbon monoxide—even over the life giving oxygen atoms (as much as 200 times as readily as oxygen) forming a toxic compound known as carboxyhemoglobyne (COHb). By replacing oxygen with carbon monoxide in our blood, our bodies poison themselves by cutting off the needed oxygen to our organs and cells, causing various amounts of damage—depending on exposure. ∗ Tel.: +386-1-47-71-315; fax: +386-1-25-18-567. E-mail address: [email protected] (J. Modic).
0378-7788/03/$ – see front matter © 2003 Published by Elsevier Science B.V. doi:10.1016/S0378-7788(03)00022-7
Indoor air quality (IAQ) refers to the effect, good or bad, of the contents of the air inside a structure, on its occupants. Usually, temperature, humidity, and air velocity are considered “comfort” rather than indoor air quality issues. Unless they are extreme, they may make someone unhappy, but they would not make a person ill. Nevertheless, most IAQ professionals will take these factors into account in investigating air quality situations. Good IAQ is the quality of air which has no unwanted gases or particles in it at concentrations which will adversely affect someone. Poor IAQ occurs when gases or particles are present at an excessive concentration so as to affect the satisfaction or health of occupants. In the minor instances, poor IAQ may only be annoying to one person. At the extreme, it could be fatal to all of the occupants of a structure. No building is perfectly sealed and so the air inside ultimately originates outside. Air pollution present in the outdoor environment will therefore enter into the building as well. Generally, pollutants present in the outdoor environment are present at a somewhat lower concentration than outside (probably 10–90% in most cases). There are several reasons for this. Some pollutants are absorbed by materials in the building. Others deteriorate or react chemically and so disappear. Still others may be filtered out by the ventila-
904
J. Modic / Energy and Buildings 35 (2003) 903–907
tion system. Also as it takes some time for the outdoor air to enter in quantities, there may be a delay from the time a contaminant appears outdoors, to when it becomes a problem indoors. Smog from outdoors reaches its peak indoors some time after the outdoor peak. Outdoor contaminants may be present indoors at a sufficient concentration to affect the occupants. Examples are pollen and mould spores from outdoors causing hay fever and allergies indoors; and high smog levels affecting occupants inside a building. Incidentally, there is no such thing as a good smog day close to a major highway (expressway/freeway).
2. Carbon monoxide poisoning [2,8] Carbon monoxide can cause neurological problems in mature persons, and learning disabilities and developmental trouble in children and can lead to miscarriage or stillbirth for women exposed during pregnancy. Because children have faster metabolic rates than adults, they require more oxygen for vital organs such as the brain and the heart. Since carbon monoxide interferes with oxygen delivery, it can lead to damage to an infant’s developing nervous system. One reason for higher CO concentration in the room is the smokers (Table 1). The average “for loading” of COHb by smokers is about 5% (see Table 1). The main problem of CO concentration is in tunnels and garages. For many years in the United States a rule of thumb of 0.155 m3 /(s per lane m) has been applied as the ventilation requirement for road tunnels. The tests conducted at the Memorial Tunnel have shown that this value is, in fact, a reasonable first pass at an emergency ventilation rate for a road tunnel in the United States. In 1975, the EPA issued a supplement to its Guidelines for Review of Environmental Statements for Highway Projects that evolved into a design approach based on keeping a CO concentration of 125 ppm (143 mg/m3 ) or below for a maximum of 1 h exposure time for tunnels located at or below an altitude of 1000 m. In Table 1 COHb concentration relative to cigarette consumptiona Cigarettes Smokers— Non-smokers— Studies per day COHb COHb 3–4 >5 5–10 11–20 11–20 >20 >20 >20 10–40 >40 30–80
3.6 4.1 5.1 6.6 6.1 6.7 7.3 5.0 5.9 6.9 11.6
2.5 1.6 2.5 2.5 1.3 1.3 2.5 0.9 1.3 1.3 0.6
Pankow et al., 1976 [7] Effenberger et al., 1957 [7] Pankow et al., 1976 Pankow et al., 1976 Castledon and Cole, 1975 [7] Castledon and Cole, 1975 [7] Pankow et al., 1976 Butt et al., 1974 [7] Goldsmith, 1974 [7] Goldsmith, 1974 [7] Smith and Landau, 1978 [7]
Mean
–
1.66
–
a
From [9].
1988, the EPA revised its recommendations for maximum CO levels in tunnels located at or below an altitude of 1500 m to the following: • maximum 120 ppm (137 mg/m3 ) for 15 min exposure time; • maximum 65 ppm (74 mg/m3 ) for 30 min exposure time; • maximum 45 ppm (52 mg/m3 ) for 45 min exposure time; • maximum 35 ppm (40 mg/m3 ) for 60 min exposure time. These guidelines do not apply to tunnels in operation prior to the adoption date. Permanent International Association of Road Congresses (PIARC) recommendation is different. Allowable concentration of carbon monoxide is 100 ppm, for the other noxious materials are: • kCOmax = 100 ppm; • kNOx max = 25 ppm; • kSmax = 7 × 10−3 m−1 (idle, 9 × 10−3 m−1 ; dangerous, 12 × 10−3 m−1 ). Outdoor air standards and regulations such as those from the Occupational Safety and Health Standards (OSHA) and the American Conference of Governmental Industrial Hygienists (ACGIH) are discussed in the section on bus terminals. At higher elevations the CO emission of vehicles is greatly increased, and human tolerance to CO exposure is reduced. For tunnels above 1500 m, the engineer should consult with medical authorities to establish a proper design value for CO concentrations. Unless specified otherwise, the material in this article refers to tunnels an altitude to 1500 m. In cities, about two-thirds of the carbon monoxide emissions come from transportation sources, with the largest contribution coming from highway motor vehicles. In urban areas, the motor vehicle contribution to carbon monoxide pollution can exceed 90%. In 1992, carbon monoxide levels exceeded the federal air quality standard in 20 US cities, home to more than 14 million people, than their uncontrolled counterparts of the 1960s. As a result, ambient carbon monoxide levels have dropped, despite large increases in the number of vehicles on the road and the number of miles they travel. With continued increases in vehicle travel projected, however, carbon monoxide levels will begin to climb again unless even more effective emission controls are employed (Table 2).
3. Connection between CO and COHb in tunnel [1–3] Referring to [2], 727 experiments on the mortal victims of CO poison (autopsy) were realized. Superficial look on the results shows anarchy. So we must find out the connection between some parameters. The main relation between CO and COHb depends on time of exposition, human activity, and altitude. The temperature of environment in all 727 cases was practically equal. If we take in account all parameters, we can find out the correlation between results, which can
J. Modic / Energy and Buildings 35 (2003) 903–907
905
Table 2 Influence of CO concentration in air on COHb concentration in blood Concentration of CO in aira
Effects, inhalation times and symptoms developed
1–2 ppm (0.0001%) 2 ppm (0.0002%) Above 2 ppm 9 ppm 15–20 ppm
Might be normal, from cooking stoves, spillage, outdoor traffic Suggested maximum long-term allowable exposure (source: some IAQ professionals) Raises questions about why CO is elevated The maximum allowable concentration for short term exposure in a living area (source: ASHRAE) Impaired performance in time discrimination (COHb: 2.0); decrease in absolute exercise time (COHb: 2.5); shortened time to angina response (COHb: 1.9); vigilance decrement (COHb: 3.0) (source: World Health Organization 13 {WHO 13}) 21% increase in cardio respiratory complaints Earlier onset of exercise-induced angina (COHb 4.96%) (source: WHO 13) The maximum allowable concentration for continuous exposure in any 8 h period, according to federal law Significant decrease in oxygen reserve available to the myocardium (COHb 10%) Slight headache, tiredness, dizziness, nausea after 2–3 h, might be life-threatening after 3 h (source: Bacharach) Frontal headaches within 1–2 h; life-threatening after 3 h Dizziness, nausea and convulsions within 45 min; unconsciousness within 2 h, death within 2–3 h Headache, dizziness and nausea within 20 min; death within 30 min Headache, dizziness and nausea within 5–20 min; quickly impaired thinking; death within 30 min Headache, dizziness and nausea within 1–2 min; thinking impaired before response possible; death within 10–15 min Death within 1–3 min
27 ppm (0.0027%) 30 ppm (0.0030%) 35 ppm (0.0035%) 75 ppm (0.0075%) 200 ppm (0.02%) 400 ppm (0.04%) 800 ppm (0.08%) 1600 ppm (0.64%) 3200 ppm (0.32%) 6400 ppm (0.64%) 12800 ppm (1.28%) a
Carbon monoxide (CO) 10,000 parts per million (ppm) = 1% by volume.
be approximated with equation in Excel software [4]. log COHb = 0.858 log kCO + 0.63 log(wfH t) − 2.30 1013.25 − 22.87H −5.255 fH = 1013.25
(1) (2)
where COHb is the COHb concentration in blood (%); t the time of exposure (min); kCO the CO concentration in air (ppm); w the activity; w = 1 for resting, w = 1.69 for walking, w = 2.81 for easy work, w = 3.77 for hard work; fH the influence of altitude; H the altitude (km). We find out that the correlation in this case is: r 2 = 0.998. After two steps (antilogarithm and differentiation) from Eq. (1), we obtain: dCOHb 0.86 (wfH )0.63 (wfH t)−0.37 (3) = 0.032kCO dt Eq. (3) is possible to solve numerical way (Runge-Kutta), or with software [5].
Fig. 1. CO concentration in tunnel.
A fire in the tunnel can be simulated, in which case a specified heat flux is added in a limited section of the tunnel. The variation of temperature along the tunnel is calculated using a function that describes how the relation between the increase of temperature in the air the time since the start of the fire.
4. CO concentration in tunnel [1,6] 4.2. The results of calculation 4.1. Available computer program For calculations we used program IDA [6]. IDA Road Tunnel Ventilation calculates air pressure, air flow, temperature as well as CO and nitrogen oxides (NOx ) contents in complex tunnel networks. The calculations are performed for a network of tunnels with an arbitrary geometry. The user enters a geometrical description of the tunnels, i.e. height and cross-section area along the length of the tunnel. Other input data are atmospheric conditions, including wind pressure, at the entrances of the tunnels, the amount of traffic through the tunnels, the emission of pollution, and coefficients of friction.
As an example we took in account a tunnel 3200 m long, with unidirectional traffic, standard geometry (A = 56 m2 ), 1000 vehicles/h, 40% of trucks, various velocities of vehicles, altitude 300 m, normal meteorological circumstances. The result of calculation is on Fig. 1 and Table 3.
5. COHb concentration in blood From Table 1 we find out, that the basic concentration of COHb in a smoker’s blood is 5% (average). This is a “for loading”. Now we solve the differential Eq. (3) by computer
906
J. Modic / Energy and Buildings 35 (2003) 903–907
Table 3 CO concentration in tunnel
v (m/s) CO (ppm)
20 km/h
30 km/h
40 km/h
50 km/h
60 km/h
70 km/h
80 km/h
90 km/h
1.45 70.70
2.30 33.60
3.20 19.80
4.00 12.80
4.80 9.50
5.60 7.10
6.40 5.60
7.10 4.60
Fig. 2. Concentration COHb (kCO , t, v), L = 3200 m, M = 1000 h−1 . Fig. 4. Concentration COHb (kCO , t), kCO = 500 ppm.
program on numerical way [5], and we take in account for loading of 5%. 5.3. The case of fire 5.1. Tunnel is 3200 m long The critical COHb concentration is 25–30% [1,2]. In this case we can see that the danger in this tunnel is rare. By velocity 20 km/h in 3200 m long tunnel the driving time is about 10 min. In this case the COHb concentration is 17%. If the time is 30 min, the COHb concentration is 25% that is the boundary level for danger. By higher velocities is the COHb concentration lower: 60 km/h → 4 min → COHb = 6% (Fig. 2). 5.2. CO concentration in tunnel is 100 ppm In this case the CO concentration is on the allowed level, the fans must be switched on. The critical time is 20 min. After 20 min the COHb concentration in blood is higher as 25% that is dangerous (Fig. 3).
The CO concentration in this case is 500 ppm at least. The problem is that also a lot of other gases are present, they are poisonous, and the visibility is low (Fig. 4). The critical time is about 5 min. In this time the COHb concentration is 25%.
6. Conclusion Concentration of carbon monoxide under level 100 ppm (0.01%) is not dangerous because the risk limit about 25% of carboxihemoglobyne appears in time longer as 20 min, except by persons with great “for loading”. Danger appear also by very high concentrations of carbon monoxide (in case of fire: 500 ppm) or if tunnel ventilation by long tunnel is out of order, but in tunnels shorter as 3000 m in normal use there are no problems.
References
Fig. 3. Concentration COHb (kCO , t), CO = 100 ppm.
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