News release

Spark from electrical switch likely ignited leaking natural gas in June 2012 valve enclosure fire near Wonowon, British Columbia

Edmonton, Alberta, 26 September 2013 — The Transportation Safety Board of Canada (TSB) released its investigation report (P12H0103) today into a natural gas fire at Spectra Energy Transmission Compressor Station N4 near Wonowon, about 160 km northwest of Fort St. John, British Columbia. The fire injured two maintenance employees.

On 23 June 2012, a fire ignited in a valve enclosure structure. The two workers were performing annual inspection work on motor-operated valves (MOVs) at the station when leaking, odorless sweet natural gas ignited. The TSB investigation determined that the enclosure structure had not been tested for the presence of flammable gas prior to the start of the work. Investigators also found that the gas was leaking due to the failure of two stem seal O-rings. Ignition of the gas likely occurred when the MOV’s CLOSE button was activated during maintenance. This action produced an electrical spark, which ignited the gas.

The investigation also noted that work permits were not consistently completed prior to the start of the work. Without a valid work permit, employees may not fully consider all potential work site hazards, increasing the risk of workplace accidents. The investigation made a finding as to risk, where it was determined that when there is a leaking valve, a notification tag should be installed at the entrance of enclosure structures to clearly communicate the potential dangers of entering the structure.

Spectra Energy has taken action to reduce the probability of reoccurrence of such accidents. Gas leak inspections have been enhanced, and leaks have been identified and repaired. Employees (management and workers) have been reminded that they must comply with safe work practices and procedures.


The TSB is an independent agency that investigates marine, pipeline, railway and aviation transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.

For more information, contact:
Transportation Safety Board of Canada
Media Relations
Telephone: 819-994-8053
Email: media@tsb.gc.ca