Good advice from MiketheEngineer regarding calling OSHA.
The scenario you described should be fine. The isolation lock can be retained close by the isolating switch on a chain or lanyard along with a Danger Tag.
If more than one worker is involved in the blade change, then each one should add their own personal isolation lock (unique key), as well as the primary isolation padlock. This can be done either with a lockout hasp or group lock box.
Check the link for a technical article on Group Lockout.
Beware the danger of legal compliance versus practical common sense. Sometimes they don't align in workplace safety. Being compliant may lull you in to a false sense of security that you are working safely. However if you apply a robust lockout procedure based on risk assessment and safe system of work, chances are you will be 'compliant'.
Compliance cannot always take into account the intricacies of the working application, which a risk assessment should identify.