At Wally’s Party Factory, a 32-store chain based in the North Texas town of Ennis, balloons no longer contain 100 percent helium — the total is down to 60 percent — and an additive is pumped in to help certain types float better.

“We’re doing a lot more to conserve the helium than we did in the past,” said Jonathan Erwin, the chain’s vice president and general counsel.

Such adjustments are one of the lighter indicators of a worldwide helium shortage. Experts say the scarcity could have significant implications for the space, high-tech and medical industries, where helium’s uses include M.R.I.’s. In a worst-case scenario, which is unlikely, the world could run out of helium in a century, said Chip Groat, a geology professor at the University of Texas at Austin.

To address the problem, Congress has proposed legislation that could have a significant impact on the Texas Panhandle, where the federal government operates the world’s largest helium production facility.