The Suncor Energy refinery in Commerce City blew black smoke into the sky after workers restarted parts of the refinery as they finished routine maintenance.
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The company issued an alert at 10:01 a.m., Tuesday that said increased smoke may be visible at its Commerce City plant because of unit startup activities.
Bright orange flames rolled from a smokestack on the southwest corner of the refinery, and plumes of black smoke billowed upward. It was business as usual as semitrailers lined up to carry fuel across Colorado and beyond.
The flames are part of the refinery’s flaring process, which burns off excess gases to avoid dangerous buildups that could result in explosions.
On July 22, Suncor notified the public that it was conducting planned maintenance activities and that visible smoke would be possible for several days.
The company twice this spring that generated public concern over excessive smoke spewing from the plant.
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In May, thick, black and yellow plumes billowed from two smokestacks at the refinery after a power outage caused the three production plants to shut down.
And in April, the refinery shut down one plant because of a possible electrical issue, sending black smoke upward.
The refinery’s emissions increase whenever workers need to shut down or restart one of the three plants at the facility.
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