Paramedics in Ottawa say that three people were taken to the hospital with mild to moderate symptoms after exposure to chemicals in a hotel swimming pool in the eastern part of Ottawa.

The Ottawa Fire Service hazardous materials team was called to the hotel on Brisebois Crescent near Centrum Boulevard at 8:48 a.m. on Saturday after fumes from chemicals mixed in a mechanical room reached the pool area, affecting several people.

The 9-1-1 caller told the dispatcher to pull the fire alarm to evacuate everyone. An OC Transpo bus was provided as shelter.

OFS said that two chemicals, about four liters of chlorine and half a barrel of muriatic acid, were accidentally mixed.

The hazardous materials team found dangerous levels of chlorine gas in the pool area.

Chlorine is commonly used as a pool disinfectant. Muriatic acid is an effective cleaning agent and is also used to lower pH and alkalinity levels in pools.

Toxic chlorine gas can be released if mixed improperly. Paramedics say six people were assessed at the scene and three were taken to the hospital.

It is unclear whether the affected individuals were guests or employees. Powerful fans were used to help clear the air.

Hazmat techs poured the chemical barrel into the pool to dilute it – a common tactic, OFS said – and took the barrel outside for disposal.

Hazardous gas levels returned to zero by 10:46 a.m. The Ottawa Fire Service evacuated the site and normal operations resumed at the hotel.