Visiting the state's air-monitoring devices on top of the City-County Health Department is not for the claustrophobic or acrophobic: you climb 20 feet up a "ladder" of metal grips that stick from the wall of a dark, narrow slot.

But while the access structures to the four monitors and their adjacent computer shack are primitive, the electronic devices they feed information to are anything but old-fashioned.New computer technology is helping Utahns breathe easier, as a tour of the Utah Bureau of Air Quality's monitoring system showed.

First stop was a main nerve center for computerized monitoring data, the main host computer, located at 261 W. Fifth South. The grungy brick building beside a fast-food outlet, adjacent to a freeway on-ramp, doesn't look like a high-tech center, yet it is.

Inside, in a small room is the state's new MV 2000, a Data General computer installed a little more than a year ago.

The earlier Data General computer--a dinosaur 15 years old--looms against a back wall. Taller than most men, it was built to use discs 15 inches wide. The old discs hold 2.5 megabites of information.

The old computer is of "very limited capacity," said Dave Prey, an environmental-health scientist who runs much of the system for the state. "It's smaller than the smallest PC they have now, in brainpower." PCs, or personal computers, are becoming common living-room furniture.

The new computer, which looks less than a cubic yard in size, has a hard disc capable of handling 160 megabites of information.

So what are all these gadgets for? Throughout the Wasatch Front from Ogden to Provo, especially in areas with serious pollution problems, the state has established about a dozen air quality monitoring stations. These stations are linked electronically to the main computer at Fifth South.

Every hour, at 6 minutes past the hour, they report the levels of carbon monoxide, sulfur dioxide, particulates (dust) and ozone. Computers also are available to monitor about four other sites.

"They're all talking, listening to each other at once," Prey said.

The main computer checks the levels reported to it against the federal ambient air standards. If it finds some standard is being violated at one of the locations, "then an alarm is sounded. It's a circuit tied in to a security company, Honeywell Security."

The Salt Lake-based company also provides more conventional security for office buildings and the like. Whenever the alarm circuit rings, it triggers an immediate response.

"Honeywell will then dial up a list of names (of officials) who are on response duty," he said. A health expert will check whether the reported violation is real.

If so, certain responses can be made, depending on how critical the situation is. If it's a Stage 1 air-pollution emergency, action is required.

At an extreme, an offending industrial plant can be shut down. "We also have the right to order mandatory restrictions on automobiles, if it's bad enough," Prey said. Car exhaust releases ozone and carbon monoxide, and the smog layer can hang heavily over a city during an air inversion.

This can threaten people with certain kinds of health problems, the very young and the elderly.

The MV 2000 also helps assemble air-quality data into report form. Information is available to the public by calling 533-7239.

"We urge people to call up, especially people who have health problems," said Art King, data quality controller for information about air quality.

Experts can watch the data as it streams into the main computer. Information transmitted in is also recorded on the remote automated monitor stations, and can be checked against the information fed into Fifth South.

King showed off an ingenious method the state has to check that data transmitted in don't reflect a voltage fluctuation in the computer. A 1.35-volt mercury battery is hooked to a computer terminal, as if were a monitor sending in data.

The battery's voltage is sent into the main computer, which shows it as a reading of carbon monoxide. As long as a precise level of CO shows up for that "monitor," the experts assume that other information is being received correctly too.

The mercury battery is used because it is long-lasting, has a relatively steady output, and tends to drop off steeply in voltage when it's used up. The sharp drop-off would signal the failure of the battery. It's changed before it's used up, anyway.

Prey said a twin to this main computer is used for air-quality modeling. "We're required to do computer modeling for the permits for all the new (air pollution) sources that come into the state to make sure they don't exceed the standards."

Actually, he said, the computer models are conservative. "They over-predict sometimes by a factor of two," he said. But by over-predicting pollution concentrations, it assures there's a margin of safety in the amount of pollution released.

Next stop, one of the monitoring stations, the one on top of the City-County Health Department, Second East and Sixth South. This is where a visitor has to climb the ladder.

Two of the monitors are new, stainless-steel objects that look like fire hydrants on the Jetsons.

They were installed to measure concentrations of the tiniest particulates, following the recent passage of standards for this sort of dust. The PM10 (for particulates 10 microns across or smaller) dust pollution is a hazard, as the small particles tend to remain lodged in the lungs, causing illness.

Relatively coarse filters in the new monitors allow only the smallest particles through. At the bottom of the system are other filters that collect the dust. The final filters have to be weighed by scientists using an extremely sensitive "microbalance."

Knowing the rate of air flow--and this is recorded by meteorological instruments also on the building's roof--then the volume of tiny particles can be calculated in terms of dust per cubic foot or air.

Two other monitors nearby check the standard pollutants. All of this data feeds into the computer shack, which was being serviced when the Deseret News visited.

Every three months, the monitors are recalibrated: tested by sending known amounts of pollutants through, then adjusted if the readings are off.

Computers in the automated shack accept data from the monitors once a second, and develop an hourly average for each pollutant, except the tiny particulates, which must be weighed separately. The data are transmitted every hour to the Fifth South main computer.

If there's a breakdown of communications, the field computers can store data for up to 20 days. But that capacity may be a relic from the old days of repeated computer failures. The new system seems remarkably reliable.

"I haven't had a single hour of down-time yet," said Prey.