Stanford University

Toxic Gas

Toxic gases are hazardous materials that can cause serious injury or death. These materials are typically shipped in compressed gas cylinders.

Classifications

The Santa Clara County Toxic Gas Ordinance (TGO) classifies toxic gases as Class I, Class II, or Class III, depending upon the material and concentration, with Class I being the most hazardous.

Per the TGO, if the quantity of a Class I, Class II, or Class III toxic gas exceeds more than one pound in a cylinder or more than two one-pound cylinders in a control area (a control area can be either a specific section of a building or an entire building), very stringent control measures and a permit from the county are required.

The use of all gases must meet Fire Code requirements; the specifics depend on the toxicity and other hazards of the gas. For more information on gas and fire emergency monitoring systems, see the Toxic Gas Alarm Systems table.

The table below helps identify what steps you should take to ensure your lab/environment is ready to support the use of toxic gases or gases with a toxic component. If you have questions, contact EH&S at (650) 723-0448 or toxicgases@lists.stanford.edu

What to do?

How to do it?

Determine if the material is regulated by the TGO.

Refer to the Stanford TGO Data Table to determine TGO classification.

For any use of a TGO-regulated material, obtain written approval from the PI and retain records for at least one year.

Follow guidance found in Restricted Chemicals & High Risk Procedures.

Obtain a permit from the county for TGO-regulated materials if more than two 1-lb cylinders will be located in a control area.

Contact EH&S’s Fire Marshal’s Office for guidance at 723-0448.

For any gas containing a toxic component, regardless of concentration or quantity:

  1. Develop a Standard Operating Procedure.
  2. Complete the Toxic Gas Purchase Questionnaire and submit to EH&S at toxicgases@lists.stanford.edu prior to every purchase.*

Review the process for creating SOPs.

*Completion of the questionnaire not required for gases used in the Stanford Nanofabrication Facility.

Santa Clara County’s Toxic Gas Ordinance
  1. In September 1990, Santa Clara County adopted the Toxic Gas Ordinance (TGO) to prevent, control, and respond to potentially dangerous conditions related to toxic gases, and to protect the public from acute exposure due to accidental releases of toxic gases.

    The TGO governs the storage, use and manufacturing of regulated materials in greater than specified threshold quantities. In addition, it contains specific provisions mandating engineering controls, protective equipment, storage requirements, emergency response plans, warning systems, and employee training, based on the type and quantity of toxic gas used.

    What are toxic gases?

    Toxic gases are hazardous materials that can cause serious injury or death. Materials regulated by the TGO are those materials which meet the following criteria:

    1.  Defined as Class I, Class II, Class III

    • Class I material has a medium lethal concentration (LC 50) in air of 200 parts per million or less by volume of gas or vapor, or two milligrams per liter or less of mist, fume, or dust, when administered to albino rats weighing 200 to 300 grams for one hour (or less if death occurs within one hour).
    • Class II material has a medium lethal concentration (LC 50) in air of at least 200 parts per million but no more than 3,000 parts per million by volume of gas or vapor, or more than 2 milligrams per liter but not more than 30 milligrams per liter of mist, fume, or dust, when administered by continuous inhalation to albino rats weighing 200 to 300 grams for one hour (or less if death occurs within one hour).
    • Class III material has a medium lethal concentration (LC 50) in air more than of 3,000 parts per million but no more than 5,000 parts per million by volume of gas or vapor, or more than 30 milligrams per liter but no more than 50 milligrams per liter of mist, fume, or dust, when administered by continuous inhalation to albino rats weighing 200 to 300 grams for one hour (or less if death occurs within one hour).

    2. And meet either of the following shipping and handling conditions:

    • They are shipped in compressed gas cylinders and the material is, becomes, or acts as a gas upon release at standard temperature and pressure
    • The material is used or handled as a gas, whether or not the material meets the definition of a compressed gas set forth in the Fire Code.

    Levels of regulation

    Santa Clara County’s Toxic Gas Ordinance (TGO) establishes three levels of regulation regarding laboratory use of toxic gases:

    • Full TGO Compliance regulations are for materials whose quantities and duration of use require operation within the full TGO and Uniform Fire Code (UFC). A permit and specific controls are required for operations involving Class I, Class II and Class III regulated materials. Activities involving these types of operations are conducted in selected facilities on the Stanford University campus. Note that if minimum threshold quantities are in use, Minimum Threshold Quantity Controls apply, per B11-384.
    • TGO Limited-Use Laboratory regulations are limited to lab and research experiments, which meet the TGO Standards for use of small quantities of gas in research for a limited period of time (30 consecutive days). A notification and approval from the county is required, along with the implementation of specific controls. For additional details, see Toxic Gas Ordinance: Laboratory and Research Facility Standard for Limited-Use.
    • A regulated material is exempt from most of the provisions of the TGO if:
      • The material has an aggregate quantity of less than 2 lbs in a control area, and the quantity in a single vessel does not exceed 1 pound
      • The material has a concentration below the Permissible Exposure Limit (PEL).
      • Flow-limiting devices and fire-extinguishing systems are required for Class I materials, regardless if an exempt quantity is used. Also, exempt quantity operations must meet all other hazardous materials handling policies and regulations.

    Non-regulated materials

    Consult Stanford University’s Toxic Gas Table to determine when a toxic gas’s concentation becomes to low that it becomes non-regulated. Operations involving non-regulated concentrations must meet all other hazardous materials handling policies and regulations. Refer to the Required Actions for Regulated, Exempt, and Non-Regulated Toxic Gases Operations Flow Chart.


Restricted Flow Orifices
  1. All gas cylinders with TGO Class I gases (except for lecture bottles) having a vapor pressure greater than 29 psi shall have a restricted flow orifice (RFO — also called a flow-restricting orifice), if available, installed. If a RFO is not available, the cylinder shall be used with a flow-limiting device. Other gas cylinders with TGO gases may require the installation of a RFO to treat gas releases to less than the IDLH. Below are pictures and a drawing of a compressed gas valve showing the location of the restricted flow orifice.



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