Zoox has halted its autonomous vehicle testing operations in Atlanta after safety drivers might have been exposed to gases such as carbon monoxide, carbon dioxide, or hydrogen sulfide inside the vehicles last month, as per TechCrunch’s findings. The incidents prompted one employee to lodge a complaint with the Occupational Safety and Health Administration, which has initiated an investigation and instructed Zoox to look into the exposures. 

Potentially 40 employees were exposed to gases in the vehicles, according to a letter from OSHA to Zoox that TechCrunch accessed, although the Amazon-owned firm claims the actual number is lower.  

Zoox reinstated at least one group of workers into a different vehicle after one of them vomited and the others reported symptoms of exposure, a contractor informed TechCrunch. He mentioned that this second vehicle might have also had toxic gases, as the workers experienced further symptoms later that day. 

“They made us go right back to work after we said we were throwing up,” Jay Davis, a contractor who fell ill in mid-August, recounted to TechCrunch. “I reached out to HR, explained the situation, and expressed that it’s wrong for y’all to send us [back out].” 

Workers noted exposure symptoms and unusual odors for much of last month until August 22, when someone phoned 911 for an employee who fell ill. The facility located in northwest Atlanta has been running at limited capacity since, with the test vehicles isolated while Zoox examined the exposures, according to two staff members. The purpose-built electric robotaxis from Zoox remain unaffected.

TechCrunch interviewed Davis, who submitted the OSHA complaint, along with one current employee and two former employees for this report. The other three were granted anonymity to address sensitive company issues and due to fears of retaliation. 

These health concerns arise as Zoox expands into new cities and enhances its operations in locations like Las Vegas and San Francisco, aiming to rival the market leader, Waymo. This rapid expansion has endangered some safety monitors. As previously reported by TechCrunch, contractors have suffered injuries due to sudden braking and evasive maneuvers in the Zoox test vehicles. Waymo has also documented similar injuries among its test drivers to OSHA.  

It remains uncertain which gases the Zoox employees encountered. Davis mentioned that he and two other sick coworkers were informed at the emergency facility that their symptoms aligned with carbon monoxide exposure. The OSHA complaint references potential carbon dioxide, or CO₂, exposure. 

In a letter to OSHA dated September 10, which TechCrunch reviewed, Zoox stated it inspected its test vehicles for CO₂ signs and replaced their 12-volt batteries. Malfunctioning batteries can emit hydrogen sulfide gas, which carries a “rotten egg” odor. Some employees who talked to TechCrunch noted they detected a similar smell in the vehicles. (After the publication of this article, Zoox informed TechCrunch that no battery damage or hydrogen sulfide gas had been found.)

Zoox identified 28 individuals who rode in six test vehicles that had an “unexplained odor,” according to its letter to OSHA. The company informed OSHA that 10 workers “voluntarily underwent medical evaluation” to “confirm whether any exposure had occurred.” In the letter, Zoox revealed it received only “one medical report indicating CO₂ exposure.”  

Zoox communicated to TechCrunch that it hasn’t discovered carbon monoxide, which is odorless, in its vehicles. The firm mentioned consulting an external medical expert to investigate the situation, asserting that the only gas detected in the affected vehicles was CO₂.   

In its OSHA letter, the company disclosed plans to install CO₂ monitors in the vehicles and indicated to TechCrunch that these devices would also be able to identify other gases like carbon monoxide and hydrogen sulfide. OSHA has now closed its investigation. 

“The safety and welfare of our Zoox test fleet operators is our top priority in this situation,” the company conveyed to TechCrunch. “We are taking ongoing, necessary, and careful actions to investigate the reported incidents as needed and support any requirements from our operators. While we thoroughly review these reports, we have halted operations of our test vehicles in this area.”  

Known risks

Vehicles emit carbon monoxide and carbon dioxide while burning fuel. These gases can infiltrate a car if there is a leak in the exhaust system; they can also accumulate if a vehicle operates in a confined space for too long. This is a sufficiently common concern that the National Highway Traffic Safety Administration investigated Ford for six years regarding reports of carbon monoxide accumulation in its Explorer SUVs. 

In its letter to OSHA, Zoox claimed it has tested the vehicles’ exhaust systems for leaks and conducted a “smoke test” for cabin breach. It did not specify whether any evidence of either was found. The company also removed all the 12-volt batteries, checked them for damage, and replaced them. It did not inform OSHA if it uncovered any indications of battery damage. 

The company keeps its test vehicles operating for most of the day, partly to maintain sensor calibration and reduce the boot time of the onboard self-driving computer. Zoox employs an exhaust-capture system at its indoor locations — similar to what’s utilized to capture truck exhaust at fire stations — designed to reduce the accumulation of harmful gases.  

Zoox customizes the Highlander SUVs used in its testing fleet. Much of the modification focuses on adding sensors and an autonomy computer. However, the company also makes additional changes, including installing an interior “snorkel” above the central infotainment display that directs air toward rear-seat passengers, as reported by the employees to TechCrunch.  

Zoox asserts that it does not alter the ventilation systems in these SUVs. However, any modification to a vehicle can heighten the risk of gases seeping into the cabin. In the Ford inquiry, the National Highway Traffic Safety Administration stated in 2023 that the highest concentrations of carbon monoxide were detected in police vehicles that had added sirens, lights, and other alterations, which can lead to sealing problems. 

Zoox stands out among notable robotaxi developers because its test fleet vehicles utilize internal combustion engines. Waymo, Tesla, Avride, and Motional all deploy electric vehicles, which do not generate exhaust fumes. May Mobility has hybrid vans in its testing fleet, and Nvidia operates a limited number of gas and electric Mercedes-Benz sedans.   

“Everybody got quiet for some reason” 

Davis and the other staff indicated that individual safety monitors began reporting potential exposure symptoms to Zoox at the start of August.  

The incidents Davis experienced on August 14 were particularly serious since four employees were riding together in the SUVs — a procedure Zoox employs while training new staff members. 

Davis recounted to TechCrunch that early signs of issues appeared that morning. 

“Everything was fine. We were all laughing and chatting, just enjoying a normal workday, and then suddenly everyone got silent for some reason,” he remarked.  

Davis recalled a colleague asking if anyone else in the SUV felt “weird.” The group was nearing their scheduled morning break at 10 a.m., and so they stopped at a Chick-fil-A. As soon as they exited the vehicle, Davis reported that one coworker began vomiting, and he and the others felt lightheaded.  

They contacted the dispatcher at Zoox’s Atlanta depot, who arranged for the SUV to be towed back to base, he stated. Meanwhile, Zoox organized an Uber to return the employees to the depot.  

“As soon as we arrived back at base, we thought, okay, since we had been unwell and mentioned feeling lightheaded, we would have a lighter duty day. Just sit down and recover,” Davis expressed. “No, they assigned us to another [test car] and instructed us to go back to work.” 

After driving throughout the afternoon, Davis reported that he and his coworkers went to a food court, where he started vomiting after just a few bites of his meal.  

Davis then contacted a representative from HireArt, the third-party contractor technically responsible for Zoox’s test drivers in Atlanta. He conveyed that the representative provided him with a workers’ compensation hotline number and advised him to contact Poison Control. Three workers went to the emergency room, where they were assessed for carbon monoxide exposure.  

Davis informed that the emergency room physician did not recognize elevated carbon monoxide levels in his body. Nonetheless, he and the others were told their symptoms matched those of carbon monoxide poisoning.  

Workers continued to fall ill in the subsequent days, as reported by all four employees who spoke to TechCrunch. On August 22, one contractor became ill enough that someone at the depot dialed 911.  

It is unclear who placed the 911 call or what transpired with the ailing worker. Concerning the four employees who reported symptoms on August 14, Zoox instructed them to undergo what it labeled as a random drug test in the following days.  

This story has been amended with fresh information from Zoox.