County health officials have called in federal investigators to examine the indoor air quality at the Great Wolf Lodge in Mason, Ohio, after a series of complaints from visitors with respiratory illnesses.

Approximately 180 complaints have been logged, with about 600 people claiming flulike symptoms, rashes, coughs and respiratory problems after visiting the resort, said Daniel Collins, director of environmental health at the Warren County Health Department in Lebanon, Ohio.

After finding chlorine levels at normal parameters and air tests passable, the health department called in the National Institute of Occupational Safety and Health for further testing. NIOSH is the only agency that can test for dichloramines and trichloramines in the air, Collins said. Chloramines are chlorine byproducts created when organic matter, such as skin and body fluids, react with chlorine.

While the number of complaints appears high, the percentage of guests calling is low, Collins pointed out. ?Out of about 60,000 people, it?s less than 1 percent,? he said. Great Wolf Lodge peaks every weekend at about 3,000 guests, with around 20 complaints.

The number, however, was enough concern for the health department to investigate.

The resort has reduced its chlorine levels and limited patron usage of the hot tubs to 15 minutes.

In addition, its ventilation capacity is 3.7 times more than the minimum required by the state code, according to a statement from Great Wolf Lodge.

More than just adjusting the vents and chemical levels is necessary to combat the problem, Collins said. Better patron hygiene must be enforced as well. People should take showers before entering the water, and avoid allowing children to urinate in the pools. NIOSH is expected to have recommendations after its investigation.