Officials say the chemical spill happened on the third floor of the west tower at 7:30 a.m.
According to authorities, a quart of acetic acid spilled inside a lab. It was used to prepare for a type of test. Officials say the chemical was immediately contained after crews threw an agent on the exposed fluid.
The Wauwatosa Fire Department responded with a HAZMAT crew and cleaned it up. Everything was reported clear after an hour.
"As was reported, only a quart was spilled and the biggest concern was that we contain it and that the vapors not spread, which was exactly what was done," Wauwatosa Fire Chief Rob Ugaste said.
Since the spill was contained immediately, it did not affect the HVAC systems. No evacuations were required and no injuries were sustained.
"In the immediate areas, we did have staff who rounded with our patients and families to make them aware of the situation. Our primary concern was the safety of our patients, families and staff and at no time during the situation was anyone at risk," Holly Colby, Administrator on-call at Children's Hospital said.
By mid-morning, all emergency crews left the scene. All operations returned to normal, and the lab where the spill occurred was ruled safe to enter.