Safety Alert for Sperian Portable Gas Monitor issued

The Safety Management Group has published a safety alert from Sperian Instruments regarding the possible malfunctioning of BioSystems PhD5 portable gas detector. The notice states that

"There is a possibility that PhD5 instruments that have the Security Beep function enabled can stop actively detecting gas while continuing to show safe readings"

The notice further states that only a "handful" of detectors may be affected but it advises users to disable the security beep in the instrument as an immediate solution to the problem. It was not clear how disabling the security beep solved the problem, perhaps it is a bug in the instruments firmware. If the security beep is enabled, apparently some instruments stop actually measuring the gas, while showing safe readings! This is a dangerous failure and users should contact Sperian Instruments to update the firmware.

More details can be found on the Safety Management Group Website.

Toxic gas monitors should be installed in all public closed spaces-not just in industrial plants!

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One imagines that toxic gas monitors are necessary to be installed only in industrial plants, not in churches. Right? Well, you’re dead wrong!
AP reports that firemen and other authorities in Madison, Wisconsin said that six people — including a toddler — got sick from carbon monoxide poisoning during a Sunday church service in Madison. Paramedics were called to attend to a 2-year-old child who was reported to be groggy . The parents of the child decided to transport the child to the hospital on their own.
Fortunately, by the time a second distress call was reported to the local Fire Department, Engine Company 4 responded, bringing along monitors to check air quality at the church. The portable Carbon Monoxide toxic gas monitors showed a CO level of 3000 ppm- more than 100 times the safe limit!
The incident shows the importance of having portable toxic gas monitors handy in all places and not just industrial plants.

How do pocket H2S monitors work?

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This post will give you a brief idea about how a pocket h2s monitor works. A pocket h2s monitor is a small instrument that is meant to be used by a worker who is working in an area that may get poisoned with Hydrogen Sulfide gas (referred to as h2s). The H2S monitor is a small portable toxic gas monitor that has a clamp at the back, so that it can be easily clamped to the worker's belt or clothes. Alternatively it can be carried in a pocket. Intrinsically Safe versions are also available which means that they can be use din hazardous areas.

The pocket h2s monitor consists of a sensor (mostly electrochemical), associated electronics (including an LCD display, buzzer, light/LED) and a housing with the clamp. It has to be calibrated with a known concentration of h2s gas in air using a standard calibration gas bottle. Every time a worker enters a confined space area that may later on allow some traces of h2s inside, the worker has to carry this monitor, so that whenever h2s ingress happens, the h2s monitor will go off, sounding a loud buzzer and flashing a red LED as a warning to escape at the earliest.
Some versions can even transmit this alarm wirelessly to a remote control room or to a host unit that may be mounted in the area. This enables the workman's colleagues to rescue him, should he be unable to escape on his own.
A typical unit looks like this (shown above).

Welcome to the Gas Monitors blog!

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Industrial Plants, especially those that manufacture chemicals, process oil & gas or in other ways store or process flammable and/or combustible materials need various kinds of gas detectors to ensure operational safety. This blog post will give a brief overview of the various kinds of gas detectors used and the technologies behind them.

Usage of gas detectors

Gas detectors are mainly used for monitoring the presence (or in some cases, the absence) of gases and vapors. If we classify gas detectors on the basis of the gas being detected, we can classify them into three types as under.

1) Toxic Gas detectors

2) Explosive Gas Detectors

3) Oxygen detectors

Note that we can use the first two types of gas detectors to detect regular gases as well as vapors that are generated by volatile liquids. The third type is generally used to check if a restricted area (also known as a confined space-like the inside of a large storage tank) contains enough Oxygen to sustain a workman who may be present in that area. In applications where Nitrogen blanketing is used to make the vapor space above an inflammable liquid inert, an Oxygen detector can tell us if the vapor space is really inert or not. Thus in these cases, we are more interested in knowing about the absence of Oxygen, rather than its presence.

Technologies

There are a few major technologies that are in usage today for detecting gases. They are listed below.

1. Catalytic Combustion type

These detectors utilize actual combustion of the gas that is to be detected, on a hot “bead” that is part of a Wheatstone bridge network of resistors. The presence of the gas causes combustion that alters the resistance and thus can be converted into an electrical signal. This is the most common type of gas detector in usage today. The same technology is used in propane detectors.

2. Electrochemical Type

In this type of gas monitor, the sensor is an electrochemical cell with an electrolyte (which may be in the form of a gel) and two electrodes. The gas that enters this cell undergoes electrolysis and a voltage difference appears across the electrodes, thus generating an electrical signal that can indicate the amount of gas. This technology is used in toxic gas detector, h2s detector and hydrogen gas detector.

3. Infrared Type

These can be point type or continuous (also known as open path). It is well known that each chemical compound absorbs infrared light of a unique band of frequencies. Also the amount is that is absorbed is in proportion to the concentration. This principle is used in infrared type gas detection.

4. Semiconductor type

In this type of gas detector, the sensor is a doped version of Silicon or Germanium, that gets its conductivity altered by the presence of a gas. This principle is used to generate a usable electrical signal.

This is a short overview of the various kinds of gas detectors used in industries and homes today.