How Google employees were exposed to toxics | March 29, 2013 | Mountain View Voice | Mountain View Online |

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News - March 29, 2013

How Google employees were exposed to toxics

Wrong HVAC setting to blame, report says

by Daniel DeBolt

All it took was a faulty HVAC system to allow toxic vapors into a pair of Mountain View buildings where over 1,000 Google employees work, according to a report released by the Environmental Protection Agency.

The buildings are above the Fairchild Semiconductor Superfund site where toxics dumped or released by the Valley's original computer chip manufacturer are evaporating from the ground — mainly trichloroethylene (TCE), classified as a human carcinogen.

The air in the buildings — part of "The Quad" at 369 and 379 North Whisman Road — must be pressurized at all hours to keep the vapors from rising through the floors. But the system to pressurize the air failed sometime last year, exposing Google employees for two months, in November and December. Levels of TCE were as high as 7.8 micrograms per cubic meter (5 is EPA's limit) — levels that require long-term exposure to cause cancer, but are high enough to cause birth defects if women are exposed during the first trimester of pregnancy, EPA toxicologists say.

The report blames a faulty pressure sensor and improper settings on the building's heating, ventilation and air conditioning (HVAC) system, the result of changes made last fall to increase the building's temperature. The EPA report concluded that "the HVAC systems were operating in a manual mode (i.e., automatic system was overridden) in order to maintain the temperature in the buildings."

The result was a negative pressure in the buildings that drew vapors inside.

Several women who were pregnant while working in the buildings expressed concerns to Lenny Siegel, director of the Center for Public Environmental Oversight. All of their babies were born healthy, he said. There may be other pregnant Google employees there as well.

"The sales folks are down there and there are a lot of women," said Google employee Helen Tsao, who doesn't work in the buildings but whose home on Evandale Avenue is close to enough to the plume that TCE vapors were found inside on Monday. "I did hear about specific incidents of pregnant women who did not want to move down there."

While elevated levels were first discovered in the buildings in November, the problem wasn't found until Jan. 14, when "(n)egative pressure was observed across all exterior doorways in both buildings." It was also found that the "tenant's (Google's) automated HVAC system was reporting erroneous pressure readings" because of a faulty pressure "transducer," or sensor.

On Jan. 19 the problem was fixed, and vapor levels were reduced to trace amounts well below EPA limits, the report says.

To keep such an incident from happening again, "technicians programmed the building static pressure sensor readings to be alarmable," the report says, adding that email messages would be sent to Google's Facilities Operations team if the pressure in the building drops.

The EPA is currently developing a long-term plan for testing the air in the buildings. Before the air was tested last year, the buildings had not been tested since 2010, said EPA spokesperson David Yogi. He added that a "sub-slab depressurization" system is being designed to draw the vapors from the soil under the buildings and exhaust them above the roofline.

Pregnant women would be particularly at risk if the HVAC systems were to fail entirely. With ventilation systems off on Jan. 1, sampling results show concentrations well above the 5 micrograms per cubic meter limit at all of the workplace test locations at 379 Whisman, with levels as high as 120 micrograms per cubic meter. At 369 Whisman, limits were exceeded at four of five of test stations in the workplace, with levels as high as 30 micrograms per cubic meter with no ventilation.

The buildings were constructed before 2011, the year that the city began requiring sub-slab depressurization systems on new buildings in the area. Records show the buildings were also tested in 2003 and 2010, and levels were below EPA limits.

Google has promised to increase efforts to alert employees to the problem, creating an internal website with information and offering to meet one-on-one with employees who are concerned. The EPA has posted the Geosyntec report on the Google buildings online at

Michelle Le contributed to this report.

Email Daniel DeBolt at


Like this comment
Posted by MtnViewOriginal
a resident of Rex Manor
on Apr 3, 2013 at 6:03 pm

I am commenting on the story "How Google employees were exposed to toxics".

I was born and raised in Mountain View. My mother said that when she moved here from Texas 47 years ago she thought she had found heaven. She explains how Mountain View was just beautiful orchards and this beautiful little tiny town. She said that in the mornings it would fog over from all the fields.

Little did we know that we would all eventually die from Cancer. My Grandmother on my fathers side came to live in her old age in an apartment off of Middlefield Road and San Antonio, and she died from Cancer. My mother bought the house in Rex Manor when I was one, I am 45 now and I have cancer. My father died from cancer. Nearly every one of their friends have died from cancer. We all just worked and lived in the area, and all are dying or have died from cancer. There are even those we know that originated in this area and moved away only to suffer the same fate with cancer. Now I know cancer is very common, but it does ring a little creepy when you think about it.

I find it hard to believe that you can put a time frame around when these toxins are released (on a certain day/month when the ventilation system was not functioning), I realize this was when the toxins were at an alarming level inside of the building, but where were these toxins before and where are they now? And for us to even single out a group "only pregnant women", and go as far as to say not really them, just their fetus'. No adults are affected? No plants or animals? So is this report trying to say that I can stand around and inhale 30 or more micro grams per cubic meters of these TCE's and nothing will happen to me? If it can bypass from the bottom of the building to be released at the top of the building then isn't it constantly being released around us? So then aren't we all in danger, and not just certain people? And what happens when these workers have to come out of their high pressure buildings? Don't they have to breathe the air outside like the rest of us?

I had this conversation with a few old mountainvieans and they seem to be sceptical. So little has been done, and so little is going to be done. Its nice that they have tests to see what the levels are, why aren't they launching some sort of counter measure as soon as this is discovered and not just discussing these things on paper comparing notes on levels?

Posted by Name hidden
a resident of Shoreline West

on May 27, 2017 at 4:17 pm

Due to repeated violations of our Terms of Use, comments from this poster are automatically removed. Why?

Sorry, but further commenting on this topic has been closed.


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