Questions to Answers
- What is the difference between Active and passive sampling?
Active sampling is different from passive sampling in that it employs an air sampling pump that serves to actively pull air and pass it through a collection device, for instance a filter. On the other hand, passive sampling does not need active air movement, like the one generated by a pump. Instead, vapors and airborne gases are collected through a physical process including permeating via a membrane or diffusion through a layer of static air.
- What is the difference between Instantaneous (real-time) and integrated (continuous) monitoring?
Instantaneous monitoring refers to the action where samples are taken from the flow and analyzed for parameters indicating the standard of industrial hygiene. On the other hand, the integrated monitoring involves samples that are taken continuously over a period of time and analyzed together. This monitoring technique gives a more representative sample for analysis. Therefore, the results derived off the integrated monitoring technique are more reliable in terms of the overall industrial hygiene standard. The instantaneous monitoring technique accounts for the standard of industrial hygiene at that point in time. it may not accounts for any changes in the standard of industrial hygiene occurring over time.
- Why do we calibrate our sampling equipment and what is the difference between a primary and secondary calibration standard. Include the types of primary and secondary calibration standards we used in lab for air sampling.
Calibration of sampling equipment is done in order to determine the relationship existing between the measurement of a known input and the output of the measuring process or a part of the measurement. In metrology, a primary calibration standard refers to a calibration standard that is satisfactorily accurate that is not subordinate to any other standard and is not calibrated in reference to any other standard. Secondary calibration standards are those instruments that are used to check equipment for biases. Secondary calibration standard is applied in relation to the primary calibration standard. While the primary calibration standard is used once in a long time, secondary calibration standards are used more frequently. An example of a primary calibration standard used for air sampling is a bubble calibrator. It measures the rate at which a soap bubble rises through a pre-determined volume. Secondary calibration standards like rotameters are used in the laboratory to calibrate air sampling equipment provided they have been calibrated according to the primary standard.
- What is the difference between flash point, LEL and UEL
There are inherent differences between the flashpoint, lower explosive limit and upper explosive limit. Flashpoint refers to the lowest temperature required for a liquid to produce enough vapor that results in an ignitable mixture. Unlike the flashpoint, the lower explosive limit is the minimum concentration of a gas in air or vapors that will combust if a source of ignition is present. On the other hand, the upper explosive limit is the maximum concentration of gas in the air or a vapor that will combust if a source of ignition is present.
- What are the different types of particulate matter?
Particulate mater consists of a suspension known as aerosols. There are different types of particulate matter. The first type is the dust that is formed through mechanical action. This type can be either organic or inorganic. The other type is fumes that are a result of a physical and chemical process that often involves a change in state. Smoke is yet another type of particulate matter. This type is formed when there is partial combustion of organic material. The other types of particulate matter are fiber and mists.
- Draw a typical particulate sampling train.
- Draw a sorbent tube sampling train without a pre-filter.
- An industrial hygienist performs personal exposure sampling for asbestos fibers in air for 480 minutes at 2.0 liters per minute. She prepares her filter for microscopic counting and counts 390 fibers per 100 fields. What is the fiber/cc amount for the exposed worker? Is this an OEL violation? (show your work)
Average exposure for 8 hours = 2.0Lminx60hrx8hrs=960L
F/mm = 390 fibers100 fields0.00753 mm2field=518 f/mm2
F/cc = 518 f/mm2960 L x 1000 cc/1L=0.21 f/m
Yes, there is an occupation exposure limit. This is because the average exposure derived above exceeds the established standards of 0.1f/cc.
- What is the difference in high flow and low flow sampling?
High flow rate involves sampling at a flow rate of above 750 milliliters of air for every minute. On the hand, low flow sampling involves obtaining an air sample at a flow rate ranging from 1 milliliter of air for every minute to 750 milliliters of air for every minute. A higher flow rate means that air from the surroundings will also be included into the sample unlike the low flow rate sampling where only air from the intended location is sampled.
- Explain the principle of chromatography.
Chromatography is a concept that refers to the separation of analyte from a mixture containing similar constituents for the purposes of qualitative and/or quantitative quantification. This method can be applied to both organic and inorganic substances. Separation through chromatography is achieved because the compounds are passed through a stationary phase while they are contained in the mobile phase. This method exploits the different rates at which compounds in a mixture interact with the stationary phase, allowing separation to occur due to the different migration rates for different analytes.
References
Bisesi, M. S., & Kohn, J. P. (1995). Industrial hygiene evaluation methods. Boca Raton, Flor: Lewis.
