Washington (CNN) — For certain workers at the Federal Aviation Administration, the government shutdown hit hardest this week with a $0 paycheck.

It’s “disheartening,” to not be paid by an employer, said Cleverson Schmidt, a radar technician based in Washington, DC.

“I’m trying to stay level, and I’m praying I don’t get a heart attack or stroke,” he said.

His job, which he is required to do even though he is not being paid, includes certifying aircraft systems for controllers to use. The equipment has to be flawless, he said. It’s how controllers make air traffic decisions with planes full of hundreds of passengers.

His family mostly relies on his income, as his wife works part-time and stays home with their son.

It broke Schmidt’s heart as a father to tell his son a month ago that he couldn’t get his allowance due to the family’s financial situation.

“Having to tell your child that you can’t provide for them is a difficult burden,” he said.

Many of these critical federal jobs were understaffed, and the people who do them overworked even before the shutdown, making the gap in pay even harder to take.

Corinne Wiseman’s husband – a controller at the Boston TRACON – supports them on his sole income, often working Thursday through Monday and then a sixth day on Tuesday, when he must pick up mandatory overtime.

“He’s not really home,” Wiseman said. “He doesn’t already see his kids hardly at all. Not his fault. It’s his schedule.”