Gas alarm for ethylbenzene
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In 2022, a fairly authoritative official account argued that ethylbenzene should be considered toxic and that gas alarms should be installed for it. 【Question 6】Should a combustible gas detector or a toxic gas detector be used for ethylbenzene leaks? 【Answer】According to the terminology definitions in Chapter 2 of the \"Design Code for Detection and Alarm of Flammable and Toxic Gases in Petrochemical Industries\" (GB/T 50493-2019), toxic gases refer to toxic gases or vaporous substances that can cause death or permanent health damage to workers during their occupational activities through skin contact or inhalation. According to Article 3.0.1 of Section 3 – General Provisions in the \"Design Code for Detection and Alarm of Flammable and Toxic Gases in Petrochemical Industries\" (GB/T 50493-2019), flammable gas detectors shall be installed in areas of production or handling facilities, as well as storage and transportation facilities, where flammable gases are used, whenever the concentration of such gases in any leaks might reach the set alarm level ； Toxic gas detectors should be installed when the concentration of toxic gases in the leaking gas may reach the alarm set value ； For single-component gas media that are both flammable and toxic, gas detectors for toxic gases should be installed ； In multi-component mixtures containing both combustible gases and toxic gases, it is possible that both the concentration of the combustible gas and that of the toxic gas could reach the alarm set points in the event of a leak; therefore, separate combustible gas detectors and toxic gas detectors should be installed. According to the Hazardous Chemicals Classification Information Table, the carcinogenicity of ethylbenzene is Category 2 ； Specific target organ toxicity – repeated exposure, Category 2 ； Inhalation hazard, Category 1. Therefore, ethylbenzene is a toxic gas, and toxic gas detectors should be installed. For reference! GB50493-2019 does not include ethylbenzene among the common toxic substances. Flammable media are included, with a lower explosive limit (LEL) of 0.8 V%. For flammable gas alarms, the first-level alarm threshold is set at 25% LEL, which corresponds to 0.2% V%, while the second-level alarm threshold is 50% LEL, corresponding to 0.4% V%. GBZ T223 specifies that the PC-STEL (allowable concentration for short-term exposure, mg/m3) is 150.
For ethylbenzene leaks, toxic gas detectors should be used. Since ethylbenzene is both flammable and somewhat toxic, with its toxicity manifesting as damage to specific target organs resulting from repeated exposure and inhalation, standards dictate that when a gas is both flammable and toxic, toxic gas detectors should be given priority. At the same time, although ethylbenzene is also a flammable gas, its carcinogenicity and specific toxicity result in higher health risks; therefore, more attention should be paid to its toxic effects. .
According to the explanations provided by several experts regarding GB 50493-2019, as well as the responses circulated online regarding the issues at the Safety and Environmental Protection Department of China Global Engineering Co., Ltd.’s Beijing branch: The Safety and Environmental Protection Department of China Global Engineering Co., Ltd.’s Beijing branch: To facilitate the design of combustible gas and toxic gas detection and alarm systems (referred to as GDS systems) in the petrochemical industry, the classification of toxic gas substances and the range of their physical properties specified in the standard **“Design Standard for Detecting and Alarming Combustible Gas and Toxic Gas in Petrochemical Industries” GB/T 50493-2019** are based on the following: 1. The gases or vapors listed in the “Catalogue of Highly Toxic Substances” (issued by the Health and Law Supervision Department under document No. [2003]142)； Note: Article 3 of the Regulations on Labor Protection in Workplaces Using Toxic Substances (promulgated and implemented on May 12, 2002) stipulates that **special controls shall be applied to the use of highly toxic substances in workplaces** ； Therefore, the gases or vapors listed in the \"Catalogue of Highly Toxic Substances\" (Wei Fa Jian Fa [2003] No. 142) fall under the scope of gas monitoring. 2. According to the standard \"Classification and Labelling of Chemicals – Part 18: Acute Toxicity\" (GB 30000.18-2013), those gases with acute toxicity classified as Category 1 or Category 2 are considered acute toxicity hazards ； Note: Based on the levels of doses that can be fatal to humans, **the acute toxicity classification standards of GHS were adopted as a reference for the classification criteria of toxic chemicals, leading to the issuance of the ‘Specifications for the Classification and Labelling of Chemicals – Part 18: Acute Toxicity’ (GB 30000.18-2013).** Practical experience shows that the acute toxicity thresholds for Category 1 and Category 2 toxic substances as specified in standard GB 30000.18 are relatively low. In the event of a leakage of such substances at a site, an environment with acute toxicity can easily develop around the source of the leakage, leading to acute occupational poisoning among workers in the area who are not wearing PPE and come into contact with these toxic gases. Therefore, the range of toxic gases defined in this standard (GB/T 50493) includes those with acute toxicity classified as Category 1 or Category 2 according to GB 30000.18-2013. [Note: Per my own research, the Hazardous Chemicals Classification Information Table (2015), which is attached to the \"Notice from the General Office of the State Administration of Work Safety on Issuing the Guidelines for the Implementation of the Catalogue of Hazardous Chemicals (2015 Edition) (Trial)\” with reference number An Jian Zong Tang Guan San [2015] No. 80, contains information that exactly corresponds to that in GB 30000.18-2013, making it convenient for reference.] Note that the ranges of acute toxicity gases in Categories 1 and 2 listed in this table are broader than those of highly toxic substances listed in the Catalogue of Hazardous Chemicals (2015 edition). 3. Toxic gases listed in the Specifications for the Installation of Toxic Gas Detection and Alarm Devices in Workplaces (GBZ/T223-2009) ； Note: The main content of GBZ/T223-2009 \"Specifications for the Installation of Toxic Gas Detection and Alarm Devices in Workplaces\" relates to the requirements for installing such devices in workplaces; these requirements must be met as part of the health-related design work in enterprises. The information on toxic gas substances listed in its appendices is of informational nature only, and therefore it is not necessary to follow it during the design of GDS systems within the scope of application of this standard (GB/T50493); it can merely be used as a reference. 4. Chemical hazardous gases listed in \"Occupational Exposure Limits for Hazardous Factors in the Workplace – Part 1: Chemical Hazardous Factors\" (GBZ2.1-2007). Note: The Occupational Exposure Limits for Hazardous Factors in the Workplace – Part 1: Chemical Hazardous Factors (GBZ2.1-2007) specifies the occupational health exposure limits for common chemical hazardous gases, with a relatively wide range. In the design of GDS systems within the scope of application of this standard (GB/T50493), only the OEL values for gases or vapors listed in the \"Catalogue of Highly Toxic Substances\" (issued by the Health and Supervision Department under document No. [2003]142) as specified in GBZ2.1-2007, as well as those for substances with acute toxicity categories 1 and 2 as defined in GB 30000.18-2013, are used to determine the alarm thresholds for GDS systems.
Refer to the explanatory notes 2 of GB/T50493-2019 \"Design Code for Detection and Alarm of Flammable and Toxic Gases in Petrochemical Industries\", as well as the minutes of the seminar on this code issued by the Sinopec Automation Design Technology Center and the National Chemical Industry Automation Design Technology Center. Determine whether a toxic gas detector is installed: 1. Identify whether the chemical is listed in the “Catalogue of Highly Toxic Substances” (Wei Fa Jian Fa [2003] No. 142) ； 2. If it is not listed in that catalog, it is necessary to determine whether it belongs to the acute toxic gases classified as Category 1 or Category 2 under GB30000.18-2013 \"Rules for the Classification and Labelling of Chemicals – Part 18: Acute Toxicity\" ； 3. Refer to the classification of hazard categories in the \"Hazardous Chemicals Classification Information Table\" provided in the \"Guidelines for the Implementation of the 2015 Edition of the Catalogue of Hazardous Chemicals\" (Safety Supervision Administration Office, Document No. Guan San [2015] 80).
The same issue applies in the \"Notice from the General Administration of Work Safety on Publishing the List of Hazardous Chemicals Subject to Priority Supervision\": the occupational exposure limit for toluene is PC-TWA (time-weighted average allowable concentration) of 50 pg/m3; PC-STEL (short-term allowable exposure concentration) is 100 pg/m3. It is also explicitly stated that \"when manual dehydration is used for toluene storage tanks, toxic gas detection and alarm devices (fixed or portable) should be installed additionally.\" Taking into account GB50493, 223, as well as the List of Hazardous Chemicals Under Strict Supervision, and combining it with current experience, petrochemical projects are generally considered to be flammable. For reference! It seems that the “Notice from the General Administration of Work Safety on Publishing the List of Hazardous Chemicals Subject to Priority Supervision” needs to be revised.
The question now is whether toxic gas detection and alarm devices listed in the \"Catalogue of Hazardous Chemicals Subject to Stringent Supervision\" should be enforced strictly; this document is of historical significance, as it was issued against the backdrop of incorporating occupational health into the safety authorities’ responsibilities. If it is to be implemented strictly, it would mean that the provisions in GBZ have to be followed, and then the definition of toxic gases in GB50493 would lose its meaning. In some places, the local safety supervision authorities have defined certain hazardous chemicals, but no one has taken action to address the issue of toxic gas detection alarms listed in the ’Catalogue of Hazardous Chemicals Subject to Special Supervision’ from a broader perspective. For example, in some places, the requirements for toluene are as follows. Set up combustible gas alarms as standard; for facilities that require manual operation, portable toxic gas alarms can be installed.
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