CALGARY -- As the Kensington Sunterra remains closed after a gas leak that sent grocery store staff to hospital, first responders are reminding Calgarians to be prepared against carbon monoxide exposure.

On Thursday afternoon seven employees were taken to hospital, three in serious condition, while another three had previously gone home for feeling ill.

Glen Price, president of Sunterra tells CTV news that everyone who received medical care was sent home later that evening to recover.

Price said the central heating unit in the basement of the building where the store is a tenant is being repaired, and added Occupational Health and Safety (OHS) officials are assisting to provide the all-clear after the malfunction.

Officials with the Calgary Fire Department say the incident could be the first of an increasing number of calls for carbon monoxide leaks with the arrival of colder weather.

“Not necessarily because we are using our furnaces or closing windows, it is more because we are discovering systems that are in a state of disrepair and aren’t functioning properly and we’re pushing them to their maximums,” said Battalion Chief Keith Stahl of the Calgary Fire Department.

He added that all heating appliances should be checked to ensure they are functioning properly, including gas fireplaces, space heaters and generators.

He recommends monthly checks on carbon monoxide detectors installed anywhere that people are spending time, and for the batteries to be replaced every year.

As for keeping the window open a crack to allow for air flow, Stahl says this is counter-productive

“It’s actually going to force your heating appliance to work that much harder to ensure that its heating the home still, if you have a malfunctioning appliance in your home, cracking the window is not going to correct the situation.”

Exposure to leaks

Stuart Brideaux, spokesperson for EMS for Alberta Health Services said an affected person might not realize they have been exposed to a leak until they present symptoms.

“By the time someone is beginning to have actual symptoms of carbon monoxide exposure or poisoning, that means they have actually inhaled or absorbed quite a dangerous amount,” said Brideaux.

The symptoms can mimic the flu, but also include headaches, dizziness, nausea and losing consciousness.

Experts on workplace safety and human resource management say after an emergency, an employer has the responsibility to communicate that safety is a priority.

“Employers have a legal responsibility to accommodate an employee in any of their health and safety concerns or requirements but only to a point of undue hardship,” said Melanie Peacock, associate professor at Mount Royal University’s Bissett School of Business.

Peacock also recommended companies create a culture that encourages clear communication, addresses prevention, good documentation of events and training where applicable.

Sunterra officials say the location could reopen in a matter of days.

Price also told CTV News he wants to make sure everyone feels safe before returning to work.