The odor was reported at about 1:50 p.m. in some areas on the second floor of the museum, located at 180 Woz Way, San Jose fire Capt. Chuck Rangel said.
Firefighters and a hazardous materials team responded to the museum and all employees and museum patrons were cleared from the building as a precaution, Rangel said. There were between 1,500 and 1,600 people in the building at the time of the report, he said.
Authorities did not find any gas, but determined the smell came from a bromide cleaning solution used in a filtration system in the basement of the museum. The odor got into the museum's ventilation system, which spread it around to various areas of the building, he said.
"Once we found that, we aired everything out, and it's not a problem anymore," Rangel said.
He said the odor never posed a health hazard, and no one was injured in the incident.
Authorities turned control of the building back to museum officials and patrons were back inside by 2:35 p.m., Rangel said.