Nitrous Oxide Leak at Pasadena Medical Building Prompts Hazmat Response

[UPDATED] Officials evacuated the parking structure of a Pasadena medical building and summoned a hazardous material response crew Friday after a leak of what was ultimately determined to be nitrous oxide, or laughing gas, authorities said.

The incident was first reported shortly before 1 p.m. in the first floor of a parking structure at 301 S. Fair Oaks Ave., according to Pasadena Fire Department officials.

The gas initially appeared to be emanating from a cylinder in a storage closet, according to fire department radio traffic.

The substance had largely dissipated by 1:30, but a hazmat team continued working to identify it and its source, city spokeswoman Lisa Derderian said.

Traffic was shut down in the area.

After the leak was stopped and the substance determined to be nitrous oxide, authorities declared the scene safe about 2 p.m., officials said.