Safety Engineering Group
ODH Compressed Gas Tool Instructions
This tool is designed to allow the user to analyze and document the Oxygen Deficiency Hazard of a room or area in compliance with the SBMS Subject Area: Oxygen Deficiency Hazards (ODH), System Classification and Controls. Specifically, this tool calculates the amount of gas that can be released from a compressed gas system and calculates oxygen levels without or with ventilation by inert (simple asphyxiant) gases. This tool is not applicable to calculate oxygen displacement by gases that liquefied under pressure, such as carbon dioxide. Contact the SME for assistance in these cases.
- Enter the information requested in the units specified.
- The system complexity assigned a failure rate to use for the fatality factor calculation. If a specific system failure rate has been determined by an engineering evaluation, that rate may be used.
- The tool will calculate the lowest concentration of oxygen possible (assumes no ventilation available) and whether an ODH Classification may be exempt.
- If ventilation is available, the tool provides the minimum time after the leak has stopped that will allow oxygen concentration to reach to a level of 19.5% (Non-ODH Atmosphere level).
- If ventilation is assumed and required for the ODH classification, the ventilation performance must be verified by Safety Engineering.
| Cylinder Size: | Select a standard size
cylinder from the menu. NOTE: If not listed, chose "Other" and enter the cylinder volume (in cubic feet) manually. Contact the SME for any help. |
| System Type | Select from the pull down menu the best description of the system. This is used to automatically fill in a system failure rate. Contact he |
| Failure Rate: | Generic system failure rates will be filled based on system
type. NOTE: If the user has established a specific failure rate (i.e. from historical data or analysis), the user can enter the system failure rate in failures per hour. |
| # of Cylinders | Enter the number of cylinders (the cylinder valve can be opened to) that are connected to the same manifold/equipment where there is a single point of failure that could cause the release of gas. |
| Cylinder Volume: |
Automatically fills in cylinder volume (in cubic feet) based on
cylinder size and # of cylinders. NOTE: If "Other" cylinder size is chosen (such as a pressure storage vessel vice DOT cylinder), cylinder volume (in cubic feet) must be manually entered. |
| Cylinder Pressure: | Cylinder
pressure in psig. This is used with
cylinder volume to calculate the volume of expanded gas at 1 atm.
(14.7 psia) NOTE: NOT APPLICABLE FOR LIQUIFIED GASES SUCH AS CARBON DIOXIDE |
| Free Room Volume (ft3) - V: | Enter the free space (air) volume of the room in cubic feet (a calculator is provided). NOTE: 1 meter = 35.3 cubic feet |
| Minimum Oxygen Concentration without Ventilation: | Calculates the Oxygen concentration if the gas freely expands in the room without any ventilation |
| ODH fatality rate (per hour) - No Ventilation: | Calculate the ODH Fatality Rate based on Oxygen Concentration and Failure Rates provided (using formulas from subject area). |
| ODH Class - No Ventilation: | Provides ODH Class based on Fatality Fact with no ventilation (worst case). |
| Minimum Room Ventilation Rate (ft3/min) - Q: | Enter room ventilation rate in ft3/min (if known). |
| Ventilation Draws In Fresh Air: | Used to determine which ventilation formula is used. Yes - Ventilation system dilutes area with fresh air (such as the building air conditioning system) No - Ventilation system draws from room (such as a fume hood or exhaust fan). |
| Leak Rate (ft3/min) - R: | Input leak rate in ft3/min of the inert gas. Typically this will be the relief valve vent rate. Examples of relief valve rates are provided
via hyderlink. Contact the SME for assistance in determining leak rate. |
| Maximum Leak Time (min): | Give time (in minutes) for the cylinder to empty based on the given leak rate. |
| Oxygen Concentration at End of Leak: | Will calculate the minimum oxygen concentration with ventilation.
NOTE: Formula from SBMS Subject Area used will be shown |
| Safe Re-enter Time (min): | Calculates the time oxygen concentration will return to 19.5%.
based on ventilation rate. (Used only to help assess potential exposure time) |
| ODH fatality rate (per hour) - With Ventilation: | Calculate the ODH Fatality Rate based on Oxygen Concentration and Failure Rates provided (using formulas from subject area). |
| ODH Class - With Ventilation: | Provides ODH Class based on Fatality Factor. |
| Calculate: | Tool performs ODH calculations when depressed. If any fields are changed, hit "Calculate" button again.. |
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