Not very famliar with all this NEC/OHSA/NRTL stuff, but I have read quite a lot, and still I can not find a satisfaying answer to this question.
I understand some stuff round safety...In Brief...
- NEC defines the rules for eletrical safety
- OHSA order (and control) that NEC rules are applied in workplaces
- In workplaces, UL Listed equipement shall be used to futfill OHSA requirement
- In non workiplace location others (AHJ/inssurance/distributor) may require to use UL Listed equipement.
- UL Listed in non workplaces is almost a marketing "nice to have".

What I can't figure out, is When do I need by product to be UL -Listed
- OHSA requires electrical conductors and equipment to be approuved : is electronic included within electrical?
- do electrical stands for anything pluged in mains and connected to electrical distribution?
- are battery powered products also considered?
- is there a voltage limit? I saw 50V-5mA once.
- Seems to me USB Mouse is not UL Listed, neither a Wireless mouse...
- So what are the keypoints to know if you got to be UL Listed?
- Connected to mains?
- Voltage & Current ?
- Use of radio function?
- Use of battery?
- Is that always up to the NRTL to decide wether your product presents some hazard and hence require to be listed?
Thanks