Alberta Environment says a 12-hour refinery flare that left a black plume visible for kilometres over Edmonton's eastern skyline didn't create a public health hazard.

Spokesman Jamie Hanlon says monitoring equipment registered no changes in air quality as the flare stack from Imperial Oil's Strathcona refinery shot flame and smoke into the atmosphere last Friday.

Imperial spokesman Jon Harding says flaring began shortly before noon and lasted until almost midnight.

He says the problem was caused by a compressor and a steam generator malfunctioning at the same time.

Air-monitoring stations in nearby Sherwood Park and east Edmonton registered no unusual changes in eight different emissions, including hydrogen sulphide and sulphur dioxide.

All air-quality parameters remained below Alberta's guidelines.

The flare caused major traffic on social media as well as on roads near the refinery as people pulled over to take pictures.