HVAC Procedure and Performance Guide

Purge air from gas line

Training for this procedure can be found in these courses:

                         131 – Oil Heat l  and  161 – Boilers l


Gas line must be pressurized from gas supply and then bled at furnace end until all air is removed from pipeline.  Gas line must be free of air before equipment is placed in operation.  Adequate ventilation must be maintained in furnace area to prevent accumulation of gas and explosive atmosphere.  Applicable safety procedures must be followed.


  1. Locate gas line, gas supply valve and furnace connection.
  2. Collect tools, equipment and materials.
  3. Put on safety and protective equipment and apparel.
  4. Disconnect electrical power to furnace.
  5. Open pipe at furnace.
  6. Open gas supply valve to pipeline and purge gas through line until all air has been removed.
  7. Ensure that furnace area is adequately ventilated and that gas does not collect in furnace area.  Use positive pressure ventilation.  Do not draw gas through fan or use spark-producing equipment in gas atmosphere.
  8. Close pipe at furnace and shut off gas.
  9. Leak test system.  (Note:  This procedure may require a standing test of several hours duration).
  10. Ventilate furnace area until all accumulated gas is removed.
  11. Reconnect electrical power, fire furnace and test operation.
  12. Leave equipment in required operating status.
  13. Remove safety and protective equipment and apparel.
  14. Gather tools, equipment and leftover materials, and leave work site clean.