At Tahoe Treetop Adventure Park, people prepare to climb into a web of cables and logs that are strung a hundred feet up.
They step in to a harness, climb up a ladder, hang from a pulley, fly through the trees, most land safely. Some don't follow directions.
"Did you grab the white rope?," an employees asks a child.
"No," the kid responds.
When people don't follow directions they get hung up on the web and staff have to save them.
"It's fun, a little scary, but that is because I am a little scared of heights." Anna Ong is one of the estimated 10,000 people who've zip-lined at Tahoe Treetop over the past three years. She says she feels safe. "Yes, for the most part, but then I got scared and came back down. I felt safer on the zip line than on the wobbly bridges."
The new popularity of zip lines has drawn the attention of California state safety inspectors. Topher Marla, Operations Manager for North Tahoe Adventures is getting letters from the state asking questions about engineering for the first time.
"The regulators are trying to understand the dynamics of our industry this is something new that they are taking on," says Marla.
She says the scrutiny is reverberating in the industry that is now employing thousands of people.
"I don't want to be the guy who comes in the next day who says sorry guys, we are out of work right now until this inspection process finishes up."
Zip line operators in California have been self-regulated for more than 15 years. Marla says he is working closely with inspectors to standardize what is now an "imperfect" process of safety reviews.