DENVER (CBS4) – There’s a hidden danger lurking inside marijuana grow houses which has caught first-responders unprepared. They are encountering alarmingly high levels of mold which poses a threat to anyone who breathes it.

Indoor grow houses are the perfect incubator for dangerous mold. A study by experts concluded those who spend time in them should wear protective clothing and respirators. But CBS4 found that’s not always the case.

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Burglars crash in, smash in and dash off with pricey marijuana plants at grow houses. And when the burglary alarms go off, police sirens are sure to follow.

(credit: CBS)

(credit: CBS)

“It’s a huge concern for us,” said Jim Gerhardt with the Colorado Drug Investigators Association.

Gerhardt says officers never know what they will encounter when they enter a marijuana grow house, including enough mold to make people seriously sick.

“One officer in particular was hospitalized for months,” he said.

Working with law enforcement, a research team from National Jewish Health entered 30 illegal grow operations and found 40 percent of them had levels that would be classified as an indoor air quality problem.

“The most conservative approach would be to wear some sort of respiratory protection,” said Mike Van Dyke, a researcher who was a part of the National Jewish study.

That was the recommendation announced at a 2012 news conference. But that’s not always happening.

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CBS4 has learned that in two separate incidents this year Denver police officers had to seek treatment after responding to burglary calls. Four officers were exposed to mold and three others were exposed to a sulfur burner used to eliminate mold. None of the officers were wearing a breathing apparatus.

“The mold was all over the facility … in the flower room, the vegetation rooms, the trim room especially,” said Justin Williams, who says he breathed mold every day when he worked in a grow house. “I was getting sick, respiratory infections, and getting reprimanded because I was not going to work (calling in sick).”

Williams wonders if the pot he was helping sell was safe.

“They are passing it off to patients and they are wondering, ‘Why I’m getting sick from something that is supposed to help me,’ ” Williams said.

The mold is showing up under the microscope. CBS4 obtained slides of moldy marijuana from a licensed testing facility.

Mold (credit: CBS)

Mold (credit: CBS)

Right now there is no mandatory testing for mold in products or in the air at grow houses.

“Who’s dealing with that? The Department of Health isn’t, the Department of Revenue isn’t,” Gerhardt said. “In Colorado’s rush to legalize we’ve encountered yet another unintended consequence, and no one is dealing with it.”

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The dangers of marijuana have been hotly debated for years, but much less has been said about the risk to law enforcement and grow house workers about the mold it helps create.