Hydrogen sulphide gas Hydrogen sulphide gas is one of the most deadly occupational hazards in drilling. It goes by many names: H2S, Sour Gas and Sulfuretted Hydrogen. People working in the oil and gas industry must be aware of its deadly properties. Sewer maintenance crews, blasters and miners have learned to respect this gas. Employers must ensure that workers who may be exposed to H2S gas are able to recognize its lethal effects. Workers should also know how to rescue and administer first aid to victims who are overcome. The purpose of this section of the site is to alert employers to the dangers involved in working with H2S and to provide guidance for controlling those dangers and to give confidence while working in affected areas such as the Far and Middle East and parts of Canada The objective of this site is not to teach old dogs new tricks,  most major operator are well familiar with the dangers of H2s and have all there plans in place. The industry is changing. Over the past 12 years I have worked for many small indigenous companies. Many are new to the oil industry and some have much to learn. It is our responsibility to continue to train others. Hydrogen-sulphide (H2s) is a gas encountered all over the world. Drilling formations with the presence of H2S can encounter some very serious problems. This section we will attempt to cover the characteristics, detection, prevention, emergency procedures, safety and first aid, and training and planning. Due to the serious nature of this gas, coupled with fear and sometimes disrespect. We will attempt to get a clear understanding. Introduction    However before starting I will tell a short but true story. Some years back "Not that many" we were drilling a known H2s area. After tripping for the bit, drilling continued. As one would expect bottoms up eventually came to surface, along with it came a lot of H2s. Constant drills had taught everybody to masks up at the first indication and of course this was done. However not everyone understood what was going on. From the time the rotary stopped turning until the time the rig was secure, the rig floor telephone never stopped ringing. Once I answer it, I cant understand a word your saying take your mask "off" A slip up such as that could cost a person their life. I have never believe in the Dog eat Dog attitude or the F*** U Jack I'm all right approach. But under H2s conditions It MUST be the attitude you take. As much as I hate to say it. If your best friend is laying out there. You do not go and assist until you are masked up.  TERMINOLOGY PPM means ( Parts Per Million) and is used for the so-called toxic gases such as Hydrogen Sulphide and Carbon Monoxide. These two gases require separate sensors because their lethal concentrations are so different - H2S is deemed dangerous above 10ppm (UK) or 15 ppm (US) whilst CO may be survivable at over 200ppm although most monitors will alarm at only 35ppm (US) 50ppm (UK). It is surprising to many to learn that a fundamental gas like methane will not explode in the presence of a flame until it reaches a very specific concentration - below a certain level the gas is deemed too lean to burn and above a certain limit the gas may be too rich to burn rather like smothering a fire with too much wood. But within what may be a narrow band, between the Lower Explosive Limit (LEL) and the Upper Explosive Limit (UEL) such gases will ignite with only the faintest whiff of a Zippo. Other gas related terms are: TLV: (Threshold Limit Value) & TWA (Time Weighted Average) both are referring to the duration of exposure to a particular atmosphere. TWA usually refers to an 8 hour working day over a 40 hour week. TLV will include this definition but also defines two other exposure limits - Short term or 15minute exposure and an absolute limit or ceiling which is the most that an individual should ever be exposed to. PEL is the (Permissible Exposure Limit) and this is a figure defined by the OSHA (US equivalent of HSE in the UK) as the legal limit of exposure for an employee. This means that they may be knowingly exposed to a known hazardous gas for no longer than a legislated maximum time. Any exposure beyond the PEL for that particular gas and the bereaved relatives can presumably sue. STEL: is a UK term meaning (Short Term Exposure Limit) and refers to a maximum concentration or percentage exposure over a 15 minute period (similar to TLV-Short Term above) IDLH means (Immediately Dangerous to Life or Health) and is not something you want to see next to a low number on a Permit before making an entry. This is because IDLH given as a percentage or PPM represents the maximum exposure level at which you could survive for 30 minutes without breathing apparatus and without incurring debilitating symptoms which would hinder your escape or even irreversibly damage your health. Thus if a gas is given an IDLH of 1ppm or .000001% you know that it's a nasty one and if your SCBA packs up when your monitor is showing 10ppm its Goodnight Vienna.