Officials suspended the disposal operations for a safety and compliance review, expected for the next seven to 10 days, said Alaine Southworth, spokeswoman for the nearby Deseret Chemical Depot in Tooele County.

EG&G Materials Inc., the plant systems contractor, initiated the review after the implementation of the tighter standards led to an increase in alarms monitoring carbon monoxide and oxygen concentrations.

The new, stricter controls were required to be in place Sept. 29, under the Maximum Achievable Controls Technology, or MACT, standard.

"This review is a sound course of action and emphasizes the Army's commitment to air quality," said Ted Ryba, acting site project manager. "It will ensure that we are fully compliant with the MACT as we finish the VX agent campaign and plan for the future mustard agent disposal."

VX agent is so powerful that a single drop on the skin can cause death within 15 minutes.

In another matter, a worker at the Tooele Chemical Disposal Facility was fired as a result of an investigation launched this summer. The employee, who worked for Battelle, EG&G's subcontractor, was accused of silencing an emergency alarm system.

The investigation, which focused on monitoring that occurred in July, had turned up several other irregularities that date back to April, officials said.

Since the furnaces were fired up in 1996, crews have destroyed over half the aging chemical weapons stored at the depot, processing more than 7 tons of nerve and blister agents. The remaining nerve agent and mustard gas stored in the Tooele County facility still surpasses the size of any other chemical weapons stockpile.

The Tooele Army installation, 40 miles southwest of Salt Lake City, is one of four American facilities destroying chemical weapons.