The mall's EziBuy store was closed today due to the fumes.
The retail outlet's spokeswoman said the store was shut for a precautionary measure.
"Staff were not comfortable with the smell," she said.
She said anyone who needed treatment received it but couldn't confirm if any of the 20 patients treated were from the store.
"They [staff] are all good and fine.
"It was more uncomfortable."
She said the store would plan to open tomorrow if the smell had disappeared.
"If staff arrived and the standards weren't up to it, we won't be opening," she said.
A spokeswoman for Ngai Tahu Property, owners of Tower Junction shopping mall, said they were working with EziBuy to to "ensure there are no more concerns regarding the cleaning of pavements at Tower Junction".
"We have been onsite doing all we can to ensure the health and well-being of EziBuy staff, shoppers and staff of other adjacent stores."
The spokeswoman couldn't confirm whether there were other stores that had shut for the day.