This question has 2 answers.
1: to become familiar with the layout, hazards, features, etc in the event of a fire, and
2: as part of the NCRRS, we have criteria we have to meet, referred to as Pre-Incident Surveys or Pre-plans. The information gathered is entered onto a "Data Sheet," and we also do a drawing of the area to show hazards, features, water supply, etc. This information is updated at least twice a year (or as needed - business change, contact information, etc) and is only used by Fire Department personnel via our mobile data computers. This information is obtained two ways: phone updates and site visits. During phone updates, CFD personnel identify themselves, give a contact number the business owner can contact for verification, and obtain specific site updates and contact information over the phone. If there are any structural changes (additions/demolitions), a site visit is required to update the drawing. During site visits, CFD personnel are required to be in a departmental uniform. If at any time a person states that they are with the fire department and are not in uniform and/or cannot show you their ID, contact 911 and request law enforcement.
Note: Pre-incident surveys are only conducted at businesses and these "surveys" are not fire inspections. However, any life safety hazards or obvious violations are forwarded to the Fire Marshal. At no time will a firefighter request to "preplan" your private dwelling (residence).