Importance of proper Gas Monitors proved in Bayer Cropscience incident

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By now, all of those of you in industry must have heard about the Bayer Cropscience incident that took place in August 2008 in Institute, W. Va. There was an explosion in the Methomyl unit and two workers were killed. Several lapses were pointed out by the US Chemical Safety Board that led to the unfortunate incident. One issue however that was not highlighted by the board but emphasized by local investigative reporters, was the non working of several toxic gas detectors in the facility. The management claimed that the detectors were disconnected from the monitoring system due to maintenance, but this itself seems wrong. Generally only one detector is removed at a time for maintenance or calibration. The next one should be removed only when the first is in place.
Secondly there were no such toxic gas detectors placed along the western side of the plant. The wind direction unfortunately on that day was from the plant's western side to its neighbors (communities staying near the plant).
The explosion that took place was very close to a tank containing the extremely toxic chemical Methyl Isocyante (MIC), the same that caused the now infamous Bhopal disaster.
All in all it just shows how seriously companies should take the selection, installation and proper operation and maintenance of gas detectors and gas monitors in their plants. If not then disasters may be looming!

Four gas monitor or PID meter? Which one do you use?

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Many people in the process industry used to use a standard "four gas" monitor for years, until the advent of PID type gas monitors. So this is just an open ended question to you all... what's your favorite meter? To the newbies, a four gas monitor is basically what it says, a portable gas monitor that can measure upto four different types of gases. These can be any mix of four sensors, or a mix of one LEL sensor (for explosive gases and vapors), an Oxygen sensor (for confined space entry) and two toxic gas sensors (say H2S and Chlorine for example). These type of four gas monitors have been used for several years and are workhorses of the plant operations and maintenance teams. However the advent of PID type meters has meant a threat to the domination of the four gas monitor. Essentially a PID meter stands for a gas monitor that uses a PID (Photoionization detector) to measure a wide range of gases. These cover most compounds found in industry such as most volatile organics and toxic gases like H2S. Many PID meters also come with a built in software and systems to automatically do datalogging and calculations of parameters like TWA, etc for regulatory compliance. Calibration is easier too, with just one gas IsoButylene being used.
So tell us what's your favorite meter- PID or four-gas?