One can capture escaped helium balloons by "fishing" with long-stringed balloons sporting tacks or rolls of masking tape (sticky side out) to bring down the elusive quarry. Much easier to ban the balloons, yet there always seem to be Really Good Reasons to bend the rule. So it's good to have a way to round up those little dogies, in case your operations person wants a good night's sleep, uninterrupted by alarm calls.
Yee-ha, as we say in Texas,
Best,
Liz Bleiberg
(with thanks to the Franklin Institute for the tack balloon idea many years ago)