You won't from CFIA, as of January 15 2019 the new regulations come into effect and they are less prescriptive than currently (so you can do it your way as long as it's safe) so this is all they have to guide you
http://www.inspectio...20880237?chap=3
Magnets
- The strength and type of magnets are appropriate to the use.
- Magnets are installed in a manner to effectively remove ferrous metal prior to, or after, certain operations (e.g.dicing, slicing or filling).
- The strength of magnets is confirmed with the use of probes or other effective devices as necessary.
- Magnets are monitored as necessary to ensure effective operation and surface exposure (e.g. adequately cleaned, metal particles removed).
The FDA slightly less
Effective measures shall be taken to protect against the inclusion of metal or other extraneous material in food. Compliance with this requirement may be accomplished by using sieves, traps, magnets, electronic metal detectors, or other suitable effective means.
https://www.accessda...21:2.0.1.1.10.5
Your best course of action is to speak with a tech at the company supplying the magnet to ensure it's capable of what you deem safe.......you could perhaps use the particle size as a basis for determine magnet strength?
http://active.inspec...introe.aspx?i=8
