With loose change in hand, Keith Burton steps up to the vending machine and makes his selection.

Burton, clinical psychology graduate student, will be relying on bagel chips to pull him through his final hours on campus.

Sarah Callaway, studio arts senior, buys a small package of cinnamon rolls from a machine for lunch with a swipe of her All Aboard card.

University of Arizona students are depositing coins into or running cards through vending machines to buy soft drinks, potato chips or chocolate bars to temporary relieve their hunger and thirst between classes.

"I was really hungry today. I usually buy a soda or juice," Callaway says about her pastry selection. She says she buys a soft drink every day and normally spends $7 a week at the machines. Callaway says she hasn't eaten in the Student Union since her sophomore year.

Burton, however, uses the vending machines about once every two weeks.

"I usually buy from the machines only if I'm desperately hungry and I don't have much time," Burton says with his bagel chips in hand.

"Buying items from vending machines per se is an impulse, but on campus it's a routine," says Michael Humphreys, manager of Student Union Vending Services.

He says getting a pastry and a soft drink in the morning or a chocolate bar before a class is routine buying for students because they are on campus all day.

About 300 vending machines are on campus, 200 of which are All Aboard accessible, he says. The machines are permanent fixtures in the Student Union, campus buildings and dormitories.

Humphreys says vending machines offer students convenience because of their location, All Aboard accessibility and product selection.

"We provide the campus community with an ideal selection of nationally known products at a reasonable price," Humphreys says about vending operations.

Students living in dormitories tend to use the machines more often those living off campus. Coronado Residence Hall has nine vending machines while Arizona-Sonora Residence Hall has 14. Some of the smaller dorms like Gila, Yuma and Maricopa Residence Halls have three to five vending machines.

Jared Gass, political science freshman and Coronado resident, spends $70 or $80 a week on chocolate bars, Snapple drinks and other vending machine items.

Gass says it is convenient because, he can get something quickly late at night and without driving.

Ghia Jacobs, undecided freshman and Arizona-Sonora resident, uses the vending machines three times a day. Jacobs says she spends $10 a week on soft drinks and gum.

Student Union Vending operates out of a warehouse at 320 N. Sixth Ave. A small vault-like room within the warehouse is a chocolate lover's paradise. A large assortment of Hershey's, Mars and Nestle chocolate bars are tucked safely away in the refrigerated room.

Potato chips, beverages, dairy and pastry products are also stored in the warehouse. For the health conscientious, Student Union Vending also carries eight or nine low- or reduced-fat products.

Also, Humphreys says "the weather has a big impact on us. During the warm weather, soft drink sales pick up and in the cold weather, pastry sales pick up."

Humphreys says Student Union Vending makes more than $1.3 million in sales a year. After paying expenses, the Union makes more than $175,000 a year in profits from the vending machines, he says.

The pricing of vending machine items is based on what Student Union Vending pays distributors for the product. Humphreys says if a product was bought for 28 to 32 cents, it is sold for 60 cents in the machines.