A power outage at the Suncor Energy refinery in Commerce City, Colorado, caused thick smoke to billow from the facility on Monday afternoon [1].

The incident highlights recurring operational instability at the plant, marking the second time in a month that the refinery has released visible plumes into the atmosphere [5].

According to reports, the outage occurred while the plant was performing maintenance [1]. This failure forced the refinery to restart its equipment rapidly, a process that generated thick black and yellow smoke plumes [1], [2]. The emissions were observed coming from two smokestacks [1].

Despite the visible nature of the plumes, air quality monitors did not detect any hazardous air quality conditions following the event [4]. Suncor Energy manages the facility in Commerce City, where the restart process led to the atmospheric discharge [1], [3].

Local residents and monitors observed the plumes on May 11, 2026 [1]. The sequence of events, from the maintenance-related power loss to the subsequent equipment startup, created the visual disturbance that alerted the community [1], [3].

“A power outage forced the refinery to restart equipment, producing thick black and yellow smoke plumes.”

The recurrence of smoke events at the Suncor facility suggests a pattern of volatility during maintenance and restart cycles. While monitors reported no immediate hazardous conditions, the frequency of these incidents often increases community scrutiny and regulatory pressure regarding the refinery's operational safety and environmental impact in the Commerce City area.