Firefighters use them. So do people who are very ill, long-wall miners, welders. Scuba divers and race-car drivers. Fire extinguisher manufacturers couldn't do without them. People who sip soda don't use them, but if the producers of their soft drinks did not, they'd be missing the fizz.

In fact, said Mel Milgrom, owner of Universal Cylinder Service Center, metal cylinders containing various gases have become so much a part of the modern scene that "they affect everyone's daily life — a lot of times unknown to them."

Maintaining the cylinders to assure safety and efficiency keeps UCS humming. Founded in 1998 to test and requalify cylinders, the company recently moved into a new, larger facility at 1839 S. 900 West after outgrowing its original site in the same neighborhood.

The larger facility provides more on-site storage and has space for four testing jackets in its hydrostatic testing station, where huge cylinders are submerged in water to remove every trace of gas. Special equipment picks them up from their "bath" and moves them to the next stage of refurbishment.

The Salt Lake company has approximately 3,000 cylinders in its shop at any given time, Milgrom said. The turn-around time for those 3,000 is about six days — some 500 per day. They range from just inches to 9 feet tall, and the maintenance for each one rests on a complex set of rules that are contained in a 50-page shop guide Milgrom compiled himself. There's no one-size-fits-all method when you're dealing with 36 types of cylinders.

"Every cylinder has its own valve and neck design," he said. "They require different settings. You have to be careful. They have to have the right thread sealants, the correct torque setting."

And the business needs an extensive inventory of various valves and other components to meet individual cylinder needs, he said.

There are no schools for these workers. UCS employees (nine at present) receive training in special courses and have to be recertified every three years.

Sometimes, the cylinders come in one or two at a time. For example, drag-car racer Jack Deschner of West Haven, Weber County, dropped in with a single cylinder that is vital to his sport. The device, run by a computer, kills the car's throttle for a half to three-quarters of a second to modulate speed.

Other times, huge cylinders can come by the hundreds in semi-trailer trucks. Pickup and post-service drop-off are vital components of the business, Milgrom said, and his company handles cylinders from several Mountain West states.