PEAK - Carpark: High CO Sensor Readings Overnight

November 9, 2021

Carbon monoxide (CO) is a toxic gas, with danger compounded as it is colourless and odourless. Safework Australia recommends a maximum exposure over eight hours to be 30 parts per million (ppm). Cars can release this dangerous emission so Car Park exhaust fans (CPEF) are used to maintain a safe environment for workers and shoppers, especially in underground car parks.


This value of 30 ppm was used on-site at a Shopping Centre in Queensland, Australia to control exposure levels. The carpark has 10 CO sensors and 3 CPEF positioned throughout the underground area. PEAK detected an issue on one particular night where some car park areas saw CO levels rising>200 ppm - well above the level recommended by Safework Australia. With further analysis, PEAK also determined that none of the fans switched on during this time, even though the levels exceeded the setpoints in the Building Management System (BMS).


An Action was raised in PEAK and the FM was notified. It was discovered that a cleaning crew was on site that night to clean the concrete. Their equipment was gas-powered and generated CO when operating.


The BMS technician was required to visit the site and test the CPEFs. CIM’s Engineers recommended ensuring that the units were not running on a time schedule that disabled them after-hours.

This is exactly what was found on-site. The fans were not faulty, they were following a setpoint of 30 ppm; but only between the hours of 7am-7pm. This meant that no matter how high the CO levels rose outside of these hours, the units were restricted from running.

All schedules were removed from the fans and they are now able to run anytime. This will reduce the likelihood of CO exposure. This event was a timely reminder that no matter how minor a sensor or fans operation is; it can still play a major role in Health & Safety.