Fire crews were called to the incident at the leisure centre in Triangle Way just before 3pm today (May 11).
A West Sussex Fire and Rescue Service spokesman said: “This was a false alarm and no one was hurt.
“It was an equipment malfunction in the plant room which is in the basement and this created smoke and set off the alarm.
“Everyone was evacuated and we re-ventilated the room and re-set the alarm.”
A spokesman from the leisure centre said: “The Triangle was evacuated this afternoon with the fire services in attendance as a precaution, due to a mechanical fault which produced smoke.
“Following safety checks all facilities are now open as normal.”
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