Safety standards in the Sterling Chemistry Laboratory machine shop where Michele Dufault ’11 died may not match industry protocol, according to machine shop supervisors at universities across the country.

Dufault died of accidental asphyxiation before 2:30 a.m. on Wednesday morning after her hair became caught in a metal lathe. Yale administrators would not answer questions Thursday about safety precautions or access standards in the lab where Dufault was working, or whether Dufault was working alone in the lab when she died. Yale is now investigating machine shop safety across the University as the federal Occupational Safety and Health Administration opens its own probe into the incident.

Currently, students may access the Sterling Chemistry Laboratory machine shop after completing a semester-long course in basic metalworking. A junior chemistry major currently enrolled in the course confirmed that students receive a code that allows 24-hour electronic access to the shop upon successful completion of the class.

The student, who asked to remain anonymous because she was not acquainted with Dufault, said her main work in the shop involves the lathe where Dufault died. She said students stay at the Sterling Laboratory’s machine shop well into the night, and often work unsupervised. She also said that her safety training class has taught personal safety measures — in particular, tying back hair and wearing tight-fitting clothing — but that the buddy system is not emphasized.

David Johnson, the shop’s supervisor, declined to comment until investigations into the accident are over when he was reached at his home Thursday night.

All five machine shop supervisors from schools around the country who spoke with the News said that they never allow students to use their facilities alone. Of the five shops, only Stanford University’s is accessible to students 24 hours a day.

“You never, ever let someone work by themselves. I don’t care if they have 25 years of experience or not. There are simply too many things that can go wrong,” said Lenny Bucholz, Arizona State University’s student shop manager.

It remains unclear whether Dufault was alone when she began her work in the machine shop or when she died. In a campuswide email Wednesday, University President Richard Levin said Dufault’s body “was found by other students who had been working in the building.”

The idea of providing 24-hour shop access to students prompted criticism from other supervisors as well. California Institute of Technology machine shop head John Van Deusen said Yale’s safety regulations “may well have been lax” in allowing students round-the-clock access without providing supervision.

“Students don’t have enough experience to work safely — they need to be monitored at all times,” said Gordon Long, a machine shop supervisor at the University of California, Berkeley. “If [Yale’s] policy is 24-hour access for students, then that scares me. I do not like that at all.”

Stanford’s student machine shop, however, currently has a similar usage policy to Yale’s, said Karlheinz Merkle, a shop supervisor at Stanford’s Physics Department machine shop. Merkle’s shop is officially open from 8 a.m. to 4:30 p.m., he said, but the facility also maintains a 24-hour policy with keycard access for certified students — most often graduate students, and rarely undergraduates, he added. But Merkle said that Stanford may alter its access policies after Dufault’s death.

Still, it is unclear whether safety standards in the Sterling Chemistry Laboratory machine shop are the norm for such facilities at Yale. Nick Bernardo, the supervisor of the machine shop in Yale’s Mason Laboratory, said that his shop can only be accessed by a handful of people. The lab is only open from 8 a.m. to 5 p.m., he said, and students can only access the shop after hours if they are supervised by a professor or experienced teaching fellow.

Generally, he said, students are only allowed to access his shop when a professor requests it — and “standards across Yale shops” prevent anyone from working in the machine shop alone.

“The main rule is no one for any circumstances is to work alone in any shop,” Bernardo said. “That’s the rule we stress over and over and over again.”

Scott Armbrust ’13, who is currently enrolled in a mechanical design class that requires him to use Bernardo’s shop in Mason Laboratory, said he felt adequately prepared to use the machinery after two sessions on safety precautions intended to introduce students to the shop and its safety protocols. Armbrust said he has not heard of students using machinery in the Mason Laboratory machine shop without supervision.

Kathy Wilson, an investigator at the Office of the Chief Medical Examiner, said her office will not be able to determine when Dufault died. Details of Dufault’s postmortem examination will not be released to the public, Wilson said, and only the Dufault family will receive the final report.