The most important point to emphasize is that it is the responsibility the contracting officer to make the commercial item determination using his/her knowledge of the item and by market research. The first place to consult is the FAR 2.101 definition of commercial items. Paragraph (6) states: "Services of a type offered and sold competitively in substantial quantities in the commercial marketplace based on established catalog or market prices for specific tasks performed or specific outcomes to be achieved and under standard commercial terms and conditions." The contracting officer must determine if protective services and firefighting meet the definition of commercial services. It might be determined that protective services and firefighting are more relevant to governmental functions than in the commercial marketplace. Firefighting is typically a local government function. On the other hand, protective services are available outside the government for certain high-profile persons who require security details (CEOs, celebrities), so the two type of services may warrant different categorization. The contracting officer can Google "protective services" to ascertain just how "substantially" those services are sold in the commercial marketplace. Another source to consider is DCMA's Commercial Item Group, established to help contracting officers with commercial item determinations. It can be reached at firstname.lastname@example.org. The DoD Guidebook for Acquiring Commercial Items is also be a helpful resource.