In letters from his prison cell at the McConnell Unit in Beeville, Susan Fenner’s son describes miserably hot and dangerous conditions. The temperature is more than 100 degrees outside, and the heat radiates through his tiny un-air conditioned box of a cell in administrative segregation.

“There’s not much circulation, and it’s just horrible,” said Fenner, who is executive director of the Texas Inmate Family Association.

Like many of the 150,000 prisoners across Texas, Fenner’s son lives without air conditioning. As the heat index statewide soars above 100 degrees day after day, inmate advocates say complaints about sweltering conditions are increasing along with concerns about prisoners’ health. A case currently pending before the U.S. Fifth Circuit Court of Appeals, though, could change the way prisons operate under the hot summer sun.

Just 19 of the 97 prison facilities run by the Texas Department of Criminal Justice are fully air-conditioned. Another 37 facilities are partially air-conditioned, and nine are ventilated with tempered air that is blown over cooled coils.

Many of TDCJ’s facilities were built before air conditioning was common. And newer prison buildings are not often constructed with air conditioning in mind, said TDCJ spokeswoman Michelle Lyons, given the unsympathetic population in question — those who have been convicted of breaking the law.

“It’s presumed taxpayers are not going to want to fund air conditioning of the units,” she said.

Medical facilities, infirmaries and geriatric units are all air-conditioned, said Lyons said. And TDCJ staff are trained to identify and treat heat-related illnesses. Inmates can buy fans from the prison commissary, and there are programs in place to help those who can’t afford to buy fans. There also are large industrial fans in common areas, Lyons said.

Of course, it’s not only inmates who suffer through the scorching temperatures. TDCJ staff, she said, work in the same conditions. “We are committed to making sure all are safe,” she said.

When temperatures skyrocket, TDCJ officials implement system-wide protocols to prevent overheating. Inmates are allowed more water, additional showers, and in some cases they can wear shorts.

But Fenner said not all the prison units apparently take those precautionary measures. Inmates and their family members are sending the association a steady stream of e-mails with complaints about the heat. While her son will probably be OK, because he is relatively young and health, Fenner said inmates with mental health problems and physical ailments could be at risk. “There are rules about how you treat animals, but they don’t apply to prisoners,” she said.

The Texas Civil Rights Project has sued the TDCJ to force the agency to better protect inmates from the heat. In 2008, the group sued on behalf of Eugene Blackmon, a 63-year-old minimum-security inmate with high blood pressure who was serving three years in the Garza East Unit in Beeville. For more than 50 consecutive days that summer, according to court pleadings, temperatures inside the unit reached levels the National Oceanic and Atmospheric Association considers cautionary or dangerous.

Blackmon, who is now out of prison, said he suffered dizziness, nausea and headaches. Even after complaints, wardens allegedly took little or no action to help. The lawsuit claim es the conditions amounted to unconstitutionally cruel and unusual punishment. “The bottom line is they can’t be having people living in an oven,” said Jim Harrington, executive director of the Texas Civil Rights Project.

Prison officials argued in court documents that Blackmon did not show he suffered physical injury and that the issue was moot since he was no longer in that prison. A judge dismissed the lawsuit, and it is now on appeal before the federal appeals court in New Orleans.

Sean Flammer, a lawyer at Scott Douglass and McConnico, said if the appeal is successful it could affect prison conditions in Texas, Louisiana and Mississippi.

“I don’t think anybody would say prison should be the most comfortable place in world,” Flammer said. “But, at same time, it’s important that the prisons don’t have inhumane conditions.”

This post originally appeared on The Texas Tribune.