It follows community complaints to the Environment Protection Authority about odours in the area on the evening of May 21 and the morning of May 22 this year.

Those incidents, along with earlier incidents involving industrial odours in the Mayfield area, are the subject of ongoing investigations by the EPA.

READ MORE:

"As part of the investigation the EPA, with Fire and Rescue NSW, conducted inspections of tanks at Koppers carbon materials and chemicals facility earlier this week," EPA director, north Adam Gilligan said.

"These inspections identified areas of concern, including unlocked and unrestrained hatches on chemical storage tank roofs that may be contributing to odours."

The prevention notice requires the company to engage an expert mechanical engineer to assess the controls on storage tanks to make sure they are installed and operating as designed.

The expert engineer will also outline any actions that should be taken to reduce the risk of odorous emissions from Koppers chemical storage tanks.

"Koppers has undertaken considerable works over the past 12 months to upgrade their fume control systems, but these recent events and our inspections this week show more could be done on the site to improve their controls, systems and procedures," Mr Gilligan said.

The prevention notice requires Koppers to critically evaluate control equipment to inform management actions that reduce risks and provide the EPA with confidence that Koppers will not impact unreasonably on the surrounding community."

The EPA amended the site's licence earlier this year to include increased stack and boundary air monitoring, and several Pollution Reduction Programs aimed at further reducing air emissions from the premises.