About 150 people were evacuated from a Palo Alto company that manufactures microwave and radio transmission devices on Monday afternoon after a water-cooling system failed, causing an abnormally hot fire in a graphite furnace, according to fire officials.
It had originally been suspected that a hydrogen tank had caught fire.
Workers at Communications and Power Industries, Inc. (CPI), located at 811 Hansen Way, had set a fire in the furnace located in the southwest corner of Building 2 to burn off residue, a normal procedure when cleaning the furnace, but a coupling that allows recirculated cooling water to keep the temperature down failed, Deputy Fire Chief Catherine Capriles said.
Residents in the Barron Park neighborhood where the company is located were not in danger and no one was injured, Capriles added.
A woman who said she has been employed at the company for many years and spoke on the condition of anonymity, said an intercom system in the building notified employees to evacuate. The woman said she could smell smoke from the second floor and as they evacuated to a parking lot.
The fire reached a temperature of 1,800 degrees, but it was lowered to 1,300 degrees in 15 minutes, the woman said.
The fire shot out of the top of the 500-gallon furnace, Capriles said. Workers quickly switched to a secondary water source from the City of Palo Alto to reduce the furnace temperature, she said.
Firefighters removed nearby small hydrogen and methane tanks as a precaution, Capriles said. Although the temperature of the furnace had gone down, at one point it rose again, she added.
A Santa Clara County hazardous-materials team was called to the scene after the blaze was put out and while firefighters worked to cool off the overheated furnace, Capriles said.
Fire crews from Palo Alto and Mountain View responded to the incident at about 1:15 p.m. Hansen Way, which was closed between El Camino Real and Page Mill Road, reopened to traffic shortly after 2:40 p.m., and workers returned to the building.
In a statement, CPI officials said the fire was located on the first floor of the company's main manufacturing building -- not in the plating shop, which is on the second floor in another part of the building. The fire "self-extinguished," according to the statement.
Firefighters remained on the scene to inspect and clean the site and declared it safe shortly after 3 p.m.
CPI has come under intense scrutiny by residents in the Barron Park neighborhood due to concerns over safety. The company, which was originally part of Varian, significantly expanded its local presence in 2006, when it consolidated its San Carlos operations in Palo Alto.
Since then, CPI on three occasions discharged hazardous materials, most recently in May 2008. That's when it released about 50 gallons of wastewater with nickel and copper into Matadero Creek.
In March, the City Council backed a plan requiring CPI to relocate the plating shop completely off campus.
• Fire quickly snuffed out at Communication & Power Industry | November 2014