codeine metabolises as an opiate.
As far as I can tell it will test positive to opiates but secondary testing will reveal it is codeine not other nastier drugs.
Don't know what the detection level is, i.e. if you had a couple of Panadeine yesterday whether you will test positive today. I believe that codeine can be traced up to about three days but whether that is true I don't know.
The cutoff level is said to be in accordance with the relevant Australian standard, but I don't know what that means.
I think the way the rules and guidance material are written is such that it is almost impossible to tell how over the counter medications will show up on a CASA damp test when used within the proper usage guidelines (up to 8 tablets for things like panadeine or nurofen extra in 24 hrs) - if they do prove positive whether the secondary test will be treated as a legitimate over the counter medication used within the appropriate dosage limits and therefore not an issue or whether they are a no go regardless of the dosage.
Obviously taking a bucket load of over the counter pain meds i.e. more than the recommended dosage - is bad, but is "proper" use ok - I don't know