News 12 is continuing its investigation into the recent Legionnaires' disease outbreak in Central Harlem – 10 years after the deadly outbreak in the South Bronx.

Steven Serrano, CEO of NYC Cooling Tower Inspections and Services, spoke with News 12 about cooling tower inspections in the city. NYC-CTIS has serviced over 500 cooling towers across the five boroughs since 2015. Serrano said his team is responsible for making sure water treatment companies are properly treating the water.

"We do the inspections, we do the Legionella testing, we do the plan writing, the certifications," he said.

He said many of the companies that treat the water in the cooling towers also conduct their own inspections.

"You don't want your student grading his own test and that's what it's coming down to. Sometimes you have the same water treatment vendor inspecting their own services," he said.

Serrano called the procedure a "self-serving system.”

"There's a need for a third-party inspector to be looking at these cooling towers," said Serrano.

Serrano said more regulation is needed to avoid future outbreak. He suggested more frequent Legionella testing, sooner than 90 days, as well as outsourcing another company for inspections and end of year certification.

A sixth death was linked to Legionnaires' disease, city officials said on Thursday. Health officials said 111 people have been diagnosed with Legionnaires’ disease with seven people hospitalized.