PARAMEDICS were seen attending to staff outside the Hamilton OTR after another carbon monoxide alert last week, where an apparent lack of effective ventilation in the drive-thru led to an unsafe level of the dangerous gas.

The evacuation in the evening of Friday, December 29 was believed to be at least the fifth time parts of the building have been subject to high levels of the dangerous gas and the third time ambulances have been called.

Car exhaust gases building up in the drive-thru led to increased concentrations of carbon monoxide entering the store, potentially endangering customers and staff.

The situation came just over a month after several staff were taken to hospital when carbon monoxide levels reached over 100 parts per million (ppm), over three times the safe limit.

WorkSafe Victoria has stated those levels of carbon monoxide can only safely be endured for 30 minutes; the baseline is 30ppm breathed in on average over an eight-hour period.

Carbon monoxide is an invisible and odourless gas - it causes the body to stop absorbing oxygen, causing headache, dizziness, vomiting and confusion at low to moderate amounts, and can lead to sudden loss of consciousness and even death at higher concentrations.

After the incident in November, the drive-thru was closed for several days and it is believed the ventilation and monitoring systems were assessed with work carried out with the intent to avoid any recurrence.

Regional OTR management were contacted but declined to comment.