Read more about the Bayer explosionINSTITUTE, W.Va. -- Bayer CropScience managers knew methyl isocyanate monitors were broken last August when they restarted a pesticide unit where up to 37,000 pounds of the deadly chemical are stored, company officials have confirmed.Bayer officials have repeatedly issued statements saying that no MIC was released during the Aug. 18, 2008, explosion and fire that killed two workers.But during an interview last week, plant officials were unable to explain exactly how they knew that to be true."We're still investigating whether, if we had a release of MIC, it would have detected that and reported it to us," said Michael Wey, the plant's environmental and safety director.Plant manager Nick Crosby downplayed the importance of the monitors, and said he is still confident no MIC was released.But Wey also confirmed that the two monitors mounted at the plant's eastern and southern fence line -- toward West Virginia State University and the Kanawha River -- were not calibrated the night of the explosion to specifically detect MIC.Wey said he didn't know if they could be adjusted to do so. "I don't know if they're physically capable of it," he said.Questions about plant air monitors were among the few questions about the August explosion that Bayer would answer during media tours of the parts of the facility last week. Bayer officials scheduled the tours as part of what they called a "new day" in plant relations with the Kanawha Valley community.Investigators from the U.S. Chemical Safety Board have been looking into the Bayer plant's monitoring systems, both inside the Methomyl pesticide unit that blew up and around the perimeter of the Institute facility."All critical alarms and safety equipment should be properly inspected and tested to verify operability prior to startup," said Daniel Horowitz, a spokesman for the Chemical Safety Board. "We do not have information to indicate why the monitors weren't functioning, but we are looking into it."In a preliminary report, CSB investigators said last month that significant safety lapses by Bayer led to the explosion inside a tank used to decompose waste Methomyl to be burned in the plant powerhouse.The explosion blew the 5,000-pound tank into the air and across the plant. CSB investigators say that only "random chance" sent it in the opposite direction from the MIC "day tank" located just 80 feet away.Bayer stores more than 240,000 pounds of MIC, the chemical that killed thousands of people when it leaked from a Union Carbide plant in Bhopal, India, in December 1984.Most of the MIC is kept in an underground storage tank on the eastern end of the plant. But some amount is transferred each evening by pipeline across the plant to the Methomyl-Larvin area, where a tank can hold up to 37,000 pounds of it for use in those units.John Bresland, a former chemical plant manager who heads the CSB, said the August incident "was potentially a serious near miss, the results of which might have been catastrophic for workers, responders and the public." Congressional investigators concluded that the incident "could have eclipsed" the Bhopal disaster.Last week, Crosby repeated Bayer's position that "there was no MIC involved in this incident."In the days after the explosion, Bayer issued several statements that said, "Monitoring of the air in and around the site by our industrial hygiene professionals showed no chemical exposure from this incident either on or off site."At a company-sponsored public meeting in October, Crosby said, "there were no harmful chemical releases" during the explosion and subsequent fire.Bresland testified during an April 21 congressional hearing that such statements by Bayer were "clearly incorrect."CSB investigators reported that the waste tank contained about 2,500 gallons of chemicals, including Methomyl, when it exploded. Chemical pipes and venting systems in the unit were also broken open, and their contents released, the CSB said."Methomyl is toxic, and its uncontrolled decomposition may release highly toxic byproducts," Bresland told a House subcommittee. "According to publicly available material safety data sheets for Methomyl, those decomposition products may include highly toxic chemicals such as methyl isocyanate, hydrogen cyanide, acetonitrile, carbon monoxide, dimethyl disulfide, nitrogen and sulfur oxides, and methyl thiocyanate."In prepared testimony for the congressional hearing, Bayer CropScience CEO William Buckner said the company's incident commander that night "continually monitored the air around the facility and detected no potentially harmful chemical emissions that might threaten the community.""Ultimately, these and other important safety measures in place to protect the MIC day storage tank and its related piping functioned as intended."And prior to the hearing, in a Feb. 20 letter to the CSB, Bayer lawyer Robert Gombar told government investigators that MIC monitoring results inside the Methomyl unit "are not recorded, but the detection of MIC in the Unit does result in an alarm in the control room."Based on all of the information available to [Bayer] at this time, there were no MIC detection alarms during or after the incident on August 28, 2008."Later, in mid-April, Wey told the congressional investigators that the MIC monitors inside the Methomyl unit were not functioning the night of the explosion."We have come to understand that the MIC analyzer array, for want of a better term, the series of analyzers to monitor MIC in the Larvin unit, that device that measures that concentration, was out of service for maintenance repair," Wey told investigators.Congressional investigators reported that Wey "was unable" to explain why the MIC monitors were out of service on the night of the explosion.Last week, Wey told the Sunday Gazette-Mail that for some period of time before the explosion -- he couldn't immediately explain how long -- the company was "getting some spuriously high readings" on the MIC monitors. Company officials believed these were "false high readings," and not real indications of MIC in the air, Wey said.The monitoring system in question consisted of a series of sampling points and a central analyzer unit. The sampling points are located around the Methomyl unit, including the area where the waste tank that exploded was located and across the plant road, where the MIC day tank stands.Wey explained that Bayer talked to the manufacturer of the monitoring system about the problem."Their recommendation to us was to send it back to them to be realigned," Wey said. "I think we were in the process of making arrangements to take it back to them."But Bayer officials said they felt comfortable starting the Methomyl unit anyway, despite the problems with the MIC monitors.At the time, Bayer was restarting the Methomyl unit after a long maintenance shutdown, officials have said. Earlier in August, Bayer had announced it was hiring 24 workers in the Larvin unit, as part of a plan to take advantage of increased global demand. Bayer uses Methomyl, which is itself a pesticide, to make Bayer's Larvin insecticide.Crosby said last week that there was no reason not to restart the Methomyl unit without the MIC monitors.The monitors, he said, are a "second-level" safety system intended to warn of any leaks, not a primary system -- such as temperature or pressure monitors on the MIC tank -- intended to prevent releases."It's not a critical instrument," Crosby said.Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.