Manage permission in SharePoint List

I have a SharePoint List that contains a list of equipment  ( an equipment represent an item in the list) and i have 3 agencies that have access to this list. Each agency has it own equipments  on which it has read write access but  it can see equipments of the other agencies on which it has only read access .

How to accomplish this goal ? 

Should I create permission for each item in my list  ? 

Thanks.