Carbon Dioxide Asphyxiation
Carbon Dioxide (CO2) is a colorless, odorless gas that is generally not toxic or reactive. Natural sources
of CO2 include outgassing from geothermally active areas, such as volcanoes. If emitted slowly through
soil, cracks and fissures in the ground, then it will flow downhill and accumulate at low elevations,
particularly in areas with geological depressions. It can impair physical and mental performance during
prolonged exposure of 3 percent and result in loss of consciousness and death at 10 percent if victims
are not given Oxygen. (Normal atmospheric concentration is .035% and is harmless.) High levels of CO2
cause asphyxiation which means the body has been deprived of oxygen. Thus, assimilation of Oxygen
by the lungs into the blood stream is blocked resulting in a continuum of symptoms depending on the
concentrations of CO2. The concentration thresholds for health effects are outlined in the table.
Health effects of respiratory exposure to carbon dioxide
(Baxter, 2000; Faivre-Pierret and Le Guern, 1983 and refs therein; NIOSH, 1981).
Exposure
limits
Health Effects
(% in air)
2-3
Unnoticed at rest, but on exertion there may be marked shortness of
breath
3
Breathing becomes noticeably deeper and more frequent at rest
3-5
Breathing rhythm accelerates. Repeated exposure provokes headaches
5
Breathing becomes extremely labored, headaches, sweating and
bounding pulse
7.5
Rapid breathing, increased heart rate, headaches, sweating, dizziness,
shortness of breath, muscular weakness, loss of mental abilities,
drowsiness, and ringing in the ears
8-15
Headache, vertigo, vomiting, loss of consciousness and possibly death if
the patient is not immediately given oxygen
10
Respiratory distress develops rapidly with loss of consciousness in 10-15
minutes
15
Lethal concentration, exposure to levels above this are intolerable
25+
Convulsions occur and rapid loss of consciousness ensues after a few
The purpose of this activity/lab is to simulate the release of CO2 and determine its effect on candles
burning at different heights. Candles require oxygen to burn. These candles might be extinguished in
the presence of high levels of CO2. Specifically, you will be measuring the time it takes for the candles to
be extinguished at different candle heights (7cm, 6 cm, 5 cm, 4cm and 3cm.)
Pre-lab Questions
1. What relationship are we looking for in this lab? Please answer this as a question.
2. The independent variable is the condition we are changing. The dependent variable is the
condition we are measuring. The control is the condition that is unchanged. Identify the
control, independent variable, and dependent variable.
3. Generate a hypothesis for this experiment.
Materials
Stop watches
Tray or shallow pan
Candles
Vinegar
Matches
Baking Soda
Vinegar
Paper towel
Tablespoon
Scissors
Procedures
1. Measure and cut the candle from its base to 7 cm. Do not include the wick in your
measurement and never cut the wick side.
2. Attach the candle to the middle of the tray by using a match to melt the bottom of the candle.
When the base of the candle starts sizzling it is ready to be quickly attached.
3. Measure 50 ml of Vinegar and carefully pour it into the tray. Do not splash and get the wick
wet.
4. Working with your partners, one person will light the candle, a second partner will start the
timer when the third person adds one tablespoon of baking soda to the vinegar. The fourth
person will record the time it takes for the candle to be extinguished.
5. Remove the extinguished candle, rinse out the tray and dry.
6. Measure and cut the candle at its base to 6 cm. Repeat the above procedure.
7. Repeat the above procedure for the measurements of 5 cm, 4 cm, and 3 cm.
8. Working as a class, collect other table’s data, average this data for the 9 or 10 groups, and
generate one average data table for the class. You may use the whiteboard up front.
9. Individually graph the relationship between height and time to extinguish the candle.
Answer the following questions in complete sentences.
1. Is there a relationship between the height of the candle and the time it took to for the candle to
be extinguished? If so, describe this relationship.
2. Did the data support the hypothesis? Use the data to support this decision.
3. Based on the results, which gas is heavier, CO2 or O2?
4. How do high levels of CO2 cause asphyxiation?
5. Describe how the results of this experiment explain what happened in the article about the killer
lake.