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Create a 2 pages page paper that discusses industrial haygene. measuring the concentration of carbon monoxide using gas detector Industrial Hygiene Lab (SFTY 315L) Lab. lab session


Before the prevailing evolution in gas detection systems, canaries were the major carbon monoxide sensors in use in coal mines. Later a preparation of iodine pentoxide and sulphuric acid was the first chemical sensor for the detection of carbon monoxide. The process followed the chemical equation below.

5CO + I2O5 H2SO4 5CO2 + I2

Early detectors were more qualitative than quantitative. Detector tubes that provide precision, accuracy and selectively are required. Dragger tubes have been made with the capacity to measure more than 300 gases and vapors (Drager 20). The draeger tube is a vial that contains chemical preparations that change color in the presence of a target gas or vapor (figure 1). The length of the stain discoloration is an indication of the measured substance. The tube is graduated in percentage carboxy hemoglobin therefore readings are done directly from the graduations.

Figure 1 Draeger Tube

The detector tubes measure air contaminants in the concentration range of occupational exposure limits. Their characterization is application dependents as illustrated in figure 2. The measurement assembly comprises of the Drager tube and pump.

Figure 2: Gas detector assembly

The gas detector pump delivers a precise volume of sample gas (usually 100mL) while simultaneously pulling it through the detector at a desired rate (figure 3). The pumps can either be short term or long term depending on user applications (Drager 25). They are dependent of external energy sources hence their diverse applications.

Figure 3 Classification Drager tubes

In order to provide greater maneuverability, an extension hose may be utilized in hard to reach areas. There is a close relationship between the Carbon monoxide content of exhaled air. The respiratory carbon monoxide test is a reliable as well as efficient method for measuring carboxyhemoglobin content of blood (Dragger 38). The aim of this experiment is given a process of determining carbon monoxide concentration.

Figure 4 suction characteristics of a drager pump


To measure the concentration of carbon monoxide in a 100mL volume of exhaled air

Instruments and Materials

3 1L sampling bags

3 resistance tubes

1 Drager pump

3 Drager tubes


The pump was routinely checked for leaks and suction capacity. Air was blown (exhaled air) into a 1L sampling bag with the aid of a resistance tube. The Drager tube, pump and were connected as in figure 5. The bellows of the Drager pump was then compressed to a maximum level and released. Suction is automatic on release of the bellows. The gas detector pump draws out air from the sample bag into the gas detector tube. Observe the length of the discoloration and read the graduations on the beaker. Carbon monoxide tube produces a light brownish green discoloration. The process was repeated two more times using different gas detector tubes.

The gas detector pump was purged of the reaction products by flush it with clean, fresh air by performing several strokes without connecting the detector tube.


Readings were directly taken from the graduation on the gas detector tubes. The readings are in % carboxyhemoglobin.

Tube 1

Tube 2

Tube 3

Tube readings (% Carboxy Hemoglobin)


It is paramount that observations are made continuously and keenly during the duration of the experiment. Evaluation of the indicator readings should be promptly done and recorded. Measurements and readings should be done in sufficient light though excessively strong UV should be avoided as it interferes with the discoloration of the chemical indicators. Comparison of discoloration can be made with a used tube to gauge degree and length of discoloration.


Drager Safety AG. Dräger-Tubes-/Cms-Handbook, 14th Ed.

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