Zoox grounds Atlanta test fleet after workers report toxic gas exposure symptoms

Exactly what gases the Zoox employees were exposed to remains unclear. Davis said he and two other workers who became sick were told at the emergency room that their symptoms were consistent with carbon monoxide exposure. The complaint filed with OSHA mentions possible carbon dioxide, or CO2, exposure. 

Zoox told OSHA in a September 10 letter, viewed by TechCrunch, that it examined its test vehicles for signs of CO2 and replaced their 12-volt batteries. Damaged batteries can produce hydrogen sulfide gas, which creates a “rotten egg” smell. Some of the employees who spoke to TechCrunch said they noticed a similar smell in the cars. 

Zoox identified 28 employees who rode in six test vehicles that had an “unexplained odor,” the company said in its letter to OSHA. Zoox told OSHA that 10 workers “voluntarily underwent medical evaluation” to “determine whether any exposure had occurred.” Zoox said in the letter that it received only “one medical report identifying CO2 exposure.”  

Zoox told TechCrunch it hasn’t identified the presence of carbon monoxide, which is odorless, in its vehicles. The company told TechCrunch it consulted an outside medical expert to help investigate the issues and that the only gas it detected in the impacted vehicles was CO2.  

In the letter to OSHA, the company said it will add CO2 monitors to the vehicles. OSHA has since closed its inquiry. 

“The safety and well-being of our Zoox test fleet operators is our primary concern in this situation,” the company told TechCrunch. “We are taking ongoing, appropriate, and cautious actions to investigate the reported events as necessary and support any needs from our operators. While we investigate these reports thoroughly, we have ceased operations of our test vehicles in this market.”  

Cars produce carbon monoxide and carbon dioxide when they burn fuel. These gases can enter a vehicle if there is a leak in the exhaust system; they can also build up if a vehicle runs inside an enclosed space for an extended period. It’s a common enough problem that the National Highway Traffic Safety Administration investigated Ford for six years over reports of carbon monoxide buildup in its Explorer SUVs. 

In its letter to OSHA, Zoox said it tested the vehicles’ exhaust systems for leaks and performed a “smoke test” for cabin intrusions. It did not say whether it found any evidence of either. The company also removed all the 12-volt batteries, inspected them for damage, and replaced them. It did not tell OSHA whether it found evidence of damage to the batteries. 

The company keeps its test vehicles running through much of a given day, in part to maintain sensor calibration and reduce the onboard self-driving computer’s boot time. Zoox uses an exhaust capture system at its indoor depots — similar to what is used to capture truck fumes at fire houses — designed to mitigate the buildup of toxic gases.  

Zoox modifies the Highlander SUVs it uses for its test fleet. Most of that work focuses on adding sensors and an autonomy computer. But the company makes other changes, too, including adding an interior “snorkel” above the central infotainment screen that pushes air toward rear-seat passengers, the employees told TechCrunch.  

Zoox said it doesn’t modify the ventilation systems in these SUVs. But making any changes to a vehicle can increase the risk that gases will leak into the cabin. In the Ford investigation, the National Highway Traffic Safety Administration said in 2023 that the highest levels of carbon monoxide were found in police vehicles that had added sirens, lights, and other modifications, all of which can create sealing issues. 

Zoox is an outlier among major robotaxi developers because its test fleet vehicles have internal combustion engines. Waymo, Tesla, Avride, and Motional all use electric vehicles, which don’t produce exhaust gases. May Mobility’s test fleet includes some hybrid vans, and Nvidia uses a small number of gas and electric Mercedes-Benz sedans.   

Davis and the other employees said individual safety monitors started reporting possible exposure symptoms to Zoox at the beginning of August.  

The incidents Davis experienced on August 14 were more acute because four workers were riding in the SUVs together – a practice Zoox uses while training new employees. 

Davis told TechCrunch the first signs of trouble appeared early that morning. 

“Everything was fine. We was all laughing and talking, you know, just having a normal workday, and then everybody got quiet for some reason,” he said.  

Davis recalled that one of his colleagues asked if anyone else in the SUV was “feeling weird.” The crew was approaching their scheduled morning break at 10 a.m., so the workers stopped at a Chick-fil-A. As soon as they got out of the car, Davis said one of his co-workers started throwing up. He and the others felt lightheaded.  

They called the dispatcher at Zoox’s Atlanta depot, who arranged for the SUV to be towed back to base, he said. Meanwhile, Zoox arranged for an Uber to take the workers back to the depot.  

“As soon as we get back to base, we’re thinking, okay, since we’ve been sick and said we was lightheaded, you know, we’re gonna have like, you know, mild duties for the day. Just sit down, you know, get yourself back together,” Davis said. “No, they put us in another and they told us to go back to work.” 

After driving all afternoon, Davis said he and his colleagues went to a food court. He started vomiting after just a few bites of his meal.  

Davis contacted a representative from HireArt, the third-party contractor that technically employs Zoox’s test drivers in Atlanta. He said the representative gave him a workers’ compensation hotline number and told him to call Poison Control. Three of the workers went to the emergency room, where they were evaluated for carbon monoxide exposure.  

Davis said the emergency room doctor did not detect elevated carbon monoxide levels in his system. But he and others were told their symptoms were consistent with carbon monoxide poisoning.  

Workers continued getting sick in the days that followed, according to all four workers who spoke to TechCrunch. On August 22, one contractor got sick enough that someone at the depot called 911.  

It’s not immediately clear who called 911 or what happened to the sick worker. As for the four employees who reported symptoms on August 14, Zoox ordered them to take what it described as a random drug test in the days that followed.