THE PRESIDENT of the Boston Carmen’s Union urged MBTA officials on Wednesday to require all passengers to wear face coverings.

Jim Evers issued a letter he sent to state transportation officials that said it was disappointing that MBTA General Manager Steve Poftak is strongly urging passengers to wear face coverings but not requiring them to do so in all cases.

In a recent interview, Poftak noted that the governor’s order on face coverings exempts people who are unable to wear a covering because of a medical condition. He also pointed out that the order doesn’t require someone claiming a medical condition to provide proof of the condition, and said the T wouldn’t be pressing the issue.

“We won’t be refusing rides to people who are not wearing face masks,” he said.

Poftak is trying to thread a needle on face coverings and social distancing at the T. Both are issues that Poftak wholeheartedly embraces, but sources say he is also worried about how to enforce them at an agency with limited manpower and resources.

Joe Pesaturo, the T’s spokesman, released a statement underscoring the fine line the agency is walking. He said the transit authority’s visual and audio messages will stress the face-covering requirement – the word “required” will be in the messages, Pesaturo said – but he also noted the governor’s order does not apply to people with certain medical conditions and the T will not ask riders to provide proof of a condition.

Evers said people with medical conditions such as chronic obstructive pulmonary disorder should use the T’s paratransit services. “We obviously support accommodations for passengers in public transit, but not at the expense of broader public health and safety, including the safety and well-being of our members,” Evers said.

As the state begins to reopen, Evers said passenger volume is going to increase. In recent weeks, he said, passenger volume on buses has risen from 80,000 to almost 100,000 a week. “MBTA drivers and operators are increasingly concerned about what reopening will mean for increased passenger volume and, as a result, the increased risk of exposure in these confined spaces,” he said. “The public mandate that masks be worn should be enforced for the sake of employee and passenger health, and the health of family members and close contacts of them. It is not enough to simply ask passengers to comply– it must be enforced.”