CHARLESTON, W.Va. -- The lead investigator into last week's fatal carbon monoxide leak at a Corridor G hotel said Monday he believes workers accidentally dislodged an exhaust pipe when the hotel's swimming pool heater was replaced at the end of December.South Charleston Fire Department Capt. Virgil White said he's investigating two swimming pool repair companies that were asked to examine the heater at the Holiday Inn Express on Corridor G.Last week, authorities blamed an exhaust pipe connected to the heater for leaking carbon monoxide into the hotel, killing a Rhode Island man and sickening at least 17 other people.White said hotel officials asked one company in mid-December to examine the hotel's faulty, older-model heater. The company, which White could not identify Monday, recommended the heater be replaced and subsequently cut off gas to the unit, he said.The hotel then chose Premier Pools of Charleston from a list of recommended companies to replace the unit with a newer model, White said.He said Premier Pools replaced the old unit at the end of December.Sometime during the initial inspection and the unit's replacement, someone "bumped into" the heater's exhaust pipe and knocked it loose, White said.The pipe, which runs from the ground floor to the roof, leaked carbon monoxide across four levels of the hotel, White said. Readings measured the gas, which is colorless and odorless, between 500 and 600 parts per million -- more than 20 times the safe limit.White said the investigation is focusing on which company allegedly dislodged the pipe."We're trying to determine if the leak was caused when the old unit was disconnected or when the new unit was connected," he said. "We need to know who had their hands on it."Not inspectedWhite said the South Charleston Fire Department did not know the new heater had been installed, because Premier Pools did not obtain the required permit from the city.As a result, no one from the city inspected the new heater, or checked if carbon monoxide was leaking out."If they had [gotten a permit], then we would have inspected it during the work and after," White said.Steve Combs, manager of Premier Pools, said Monday he did not seek a permit because he was called to do a routine filter change at the hotel pool.Combs said his company did not install the new heating unit."Somebody had put a brand-new unit in," he said. "I have a copy of the invoice. We did not replace the unit."Combs said someone from the Holiday Inn Express called his company to replace the filter and plumbing running to the heater when the previous repairman quit before finishing the job.Combs said the hotel told him the previous repairman became frustrated while installing the unit in the cramped room because he could not maneuver around with the heater's bulky filter."The filter was so big you couldn't shut the door," Combs said.White said he did not know about the previous repairman, and identified Premier Pools as the company that installed the unit."We got receipts of work done so we know who's done what," White said.Combs said his company never touched the exhaust pipe and did nothing to the heater that could have dislodged it."I can't see any way what we did would have caused a problem," Combs said.Premier Pools has done plenty of work around Charleston and has always received the necessary permits, he said."If I know something needs a permit, I go and get it," said Combs, who called the work at the Holiday Inn Express a routine job."When I say routine, I don't mean to downplay the tragedy that happened," he said. "We were finishing something some other guy started before we got there."After installing the filter, Combs said his company did not test for the presence of carbon monoxide after switching on the unit.Two weeks beforeOn Jan. 21, about two weeks before the fatal leak, the South Charleston Fire Department was dispatched to the hotel because a fire alarm.When they got there, White said, firefighters determined that condensation from the swimming pool set off the alarm.Last week, a Randolph County woman wrote to InterContinental Hotels Group, the corporation that owns Holiday Inn Express, expressing concern about her stay at the hotel.Lori Burnside of Montrose and her friend said fire alarms went off multiple times on Jan. 21. The women feared the alarms were triggered by carbon monoxide as hotel staff opened doors to ventilate the pool."The thing that stuck in my mind was the [front desk clerk] acknowledged there was a problem with the pool and that the problem was causing the alarm to go off," Burnside told the Gazette last week.White said condensation from swimming pools frequently set off fire alarms. Fire alarms do not detect the presence of carbon monoxide and the hotel does not have any carbon monoxide detectors, he said."When condensation builds up from heat like steam, it mimics smoke," he said.He said firefighters did not test for carbon monoxide during their investigation into the activated alarms."None of that was a factor," he said.White said he expects the investigation to be completed within the next few weeks.Reach Travis Crum at email@example.com or 304-348-5163.