Are there any guidelines specifically for tertiary packaging plants?

My company manufacturers paperboard slip sheets that are placed on hardwood pallets as a protective moisture and dirt barrier for the bottom layer corrugated boxes containing food. We are not food safety certified, but are being asked for a 3rd party audit for food safety by a customer. 

I've had some experience in previous positions of corrugated box manufacturing and warehousing with AIB Certifications, which seemed to focus on a formal pest control program, cleanliness of the facility, and proper storage of chemicals to prevent any contamination. The corrugated boxes are typically secondary packaging, so higher risk than the tertiary packaging like slip sheets, pallets, unit strapping or stretch film. Are there any guidelines specifically for tertiary packaging plants?