Baggage handlers and airplane cleaners at the Phoenix Sky Harbor International Airport say they are exposed to brutally hot temperatures and are asking for an investigation into their employer.

Nearly a dozen workers wrote to the Arizona Division of Occupational Safety and Health to say that even on the overnight shift, temperatures spike to unsafe levels while cleaners work inside airplanes without air conditioning.

"These aircraft are parked and powered off on the tarmac, which continues to radiate heat and warm the uncirculated air in aircraft cabins after sunset," the letter reads.

They asked the agency to conduct an inspection of their employer, Prospect Airport Services.

CNN has contacted Prospect and the Arizona Division of Occupational Safety and Health for comment.

The letter also says break rooms are hot, and there is limited access to water.

"I've been told explicitly we can't bring water on the planes with us, and we can be in planes for as long as 30 minutes, and we're rushing to each one back to back, so we can go long stretches of time without a water break," one employee is quoted as saying.

The complaint, from a state that experienced extreme hot temperatures throughout the summer, follows years of complaints from flight attendants and other workers who want more regulations around hot planes.