The 12 Days of Gas Detection

On the tenth day, I researched the industry to discover several other instrument accessories, such as an extended run-time battery for those who work longer shifts.

• By Joe Buckley
• Dec 01, 2012

Days 1-6: Sensors, Calibration, Readings
On the first day of Christmas, my supervisor said to me, "Learn about the sensors in our gas detectors to make our employees and visitors safer." I researched the sensors utilized in our instruments and discovered we have two types of sensors: catalytic diffusion sensors (LEL) to detect flammable and combustible gases and electrochemical sensors to detect toxic gases and oxygen in our environment.

On the second day of Christmas, my supervisor asked of me, "Do we have the correct sensors in our instruments for the monitoring of gases at our facility? If we have a toxic gas present, do we monitor for the gas, or do we monitor for low oxygen? Is it advisable to use a catalytic diffusion sensor to monitor flammable and combustible gases when we use inert gases to purge our pipelines?" We purge our pipelines and confined spaces with nitrogen or argon gas to perform the "hot work." We should monitor the ambient oxygen in the atmosphere. A good practice to follow is to place an oxygen sensor and catalytic diffusion sensor in a multigas monitor, which allows us to monitor for both low oxygen and combustible or flammable atmospheres.

On the third day of Christmas, my supervisor asked of me, "How often do you bump test your instrument?" A bump test is the process of exposing an instrument's sensors to a known gas concentration to verify the sensors' performance and the alarm operation. Manufacturers' recommendations vary, but many recommend that their instruments be bump tested before each day's use.

On the fourth day of Christmas, my supervisor asked of me, "Why do we calibrate our instruments?" Instruments are calibrated to a certified known quantity of gas once a month to ensure maximum accuracy and performance. Over a period of time, with use and exposure to gases, sensors can lose their sensitivity, and by calibrating the sensors, we can ensure the sensors are working correctly.

On the fifth day of Christmas, my supervisor asked of me, "What are the calibration gases we use to bump test and calibrate our sensors?" The calibration gases we use are from a reputable company that has the gas cylinders tested by the National Institute of Standards and Technology (NIST). The gases in the cylinder match the criteria set by the manufacturer for their sensors. Our oxygen sensor is calibrated to fresh air, 20.9 percent oxygen.

On the sixth day of Christmas, my supervisor asked of me, "What are the readings on the instrument's display?" The readings are the units of measurement listed beside the sensors. The acronym for parts per million is "ppm." To understand ppm, imagine one box in a room of 1 million boxes. This unit of measurement is associated with toxic gases, such as hydrogen sulfide and carbon monoxide. %LEL is the unit of measurement for combustible and flammable gases. %Vol is the unit of measurement for oxygen.

Days 7-12: Regulators, Data, Accessories
On the seventh day of Christmas, my supervisor asked of me, "Who are the regulatory bodies that govern and oversee how our instruments function?" Our instruments are regulated by an alphabet soup of acronyms. The Occupational Safety and Health Administration (OSHA) is responsible for establishing safety and health laws for industry in the United States. The National Institute for Occupational Safety and Health (NIOSH) is the research and educational agency concerning gas detection and respiratory protection. The American Conference of Governmental Industrial Hygienists (ACGIH) is a non-profit group of industrial hygienists who disseminate research, education, and scientific information. Their purpose is to advance occupational and environmental health, and their core values are to care for the health and well-being of industrial workers.

On the eighth day of Christmas, my supervisor asked of me, "What do the acronyms on my instrument represented?" TWA stands for "Time Weighted Average," and STEL stands for "Short Term Exposure Limit." Both TWA and STEL are exposure standards set by OSHA and NIOSH. TWA is the average amount of toxic gas a worker can be exposed to over a specified time range, usually an eight-hour day. STEL is the amount of toxic gas a worker can be exposed to over a 15-minute period without risking long-term health effects.

On the ninth day of Christmas, my supervisor asked of me, "Will you check the alarm setting on my instrument?" I consulted NIOSH and OSHA standards and discovered the regulatory settings. I entered into the configuration menu of my instrument to check and confirm that my instrument had the same settings as required by OSHA.

On the tenth day of Christmas, my supervisor asked of me, "What are the accessories that come with our instruments?" I explained that the instruments come in a four-gas configuration with a standard run-time battery, battery charger, and a calibration cup with tubing. I researched the industry to discover several other instrument accessories, such as an extended run-time battery designed for employees who work longer shifts. Instruments also can be purchased with pumps to use for gas monitoring in confined spaces. Another accessory that accompanies the instruments is the docking station that performs bump tests, calibrations, diagnostics, data download from the instrument, and recordkeeping of all information required by regulatory authorities.

On the eleventh day of Christmas, my supervisor asked of me, "How do we analyze, store, and review the records collected on our gas detection instrument?" I reasoned we should let a docking station store our data records. Storing the records on a computer simplifies the retrieval of the records and also removes the problem of maintaining hard copies, illegible penmanship, and incorrect calculations. The concerns of translating the records or finding mistakes in the calculations of exposure rates to our workers are eliminated by using a docking station to store the data. In addition, we will not have to worry about missing scheduled events such as calibrations and bump tests because they are automated with docking stations.

On the twelfth day of Christmas, my supervisor said to me, "If we adhere to the information you gave me regarding our gas detection program, everyone in our facility will be safe. Strong gas detection programs can ensure a safe workplace for everyone, and thus, everyone will have a very merry Christmas and a happy holiday season."

This article originally appeared in the December 2012 issue of Occupational Health & Safety.