It's a process that can result in toxic fumes and explosions, leaves behind a dangerous trail of chemicals, and renders uninhabitable the room used for the process.
City Homeland Security Chief Inspector Joe Sullivan said a 26-year-old Philadelphia-area man who rented the room Friday night was in custody and would probably be charged, with another suspect being sought by the Narcotics Unit.
Most guests were provided shelter in the neighboring Convention Center, Sullivan said, and were able to return to their rooms by about 8 a.m., with the exception of seven rooms kept vacant for the difficult and expensive cleanup.
The hotel has 250 room and was about 60 percent full Friday night, a hotel worker said.
Hotels and motels are increasingly used by meth makers because the chemicals used - which can include lighter fuel, lye, lithium and acetone, among other dangerous substances - seep into fabrics, furniture and floors, according the Department of Justice website.
The single-pot method uses a combination of chemicals that are shaken up in a plastic bottle, with explosions sometime resulting.
Professional cleaners are required to come in to make the room safe. That will be overseen by the Department of Licenses and Inspections and the hotel.
"It's popular to do this," Sullivan said. "You basically destroy someone's hotel room, and then you leave."
Some of the guests were out-of-town firefighters, in town for the International Association of Firefighters convention that ended Thursday, Sullivan said.
Sullivan said the incident was an unneeded black eye for the city at the height of tourist season.
"Certainly, it is really disturbing that this is the experience they have in Philadelphia," he said. "The actions caused a lot of damage, and not all of it is tangible, but its serious nonetheless."
Had authorities not found out about the lab and the men had conducted their business without detection, the chemical residues would have presented a danger to any subsequent guests, especially children.
"Thank God we're aware of what occurred in there," Sullivan said. "This is a very serious matter that had very serious implications for the future."