These are automatic <a href=”http://dcra.dc.gov/DC/DCRA/Inspections/Proactive+Inspections”>proactive inspections</a>. They are looking for building/fire/health code violations that may or may not be apparent or reported by residents.
Technically, you do need to let the inspector in; otherwise they can come back with an administrative warrant. It really is not a big deal. You don’t have to be there unless you feel you can’t trust your landlord/building staff in your unit without you being present. Put valuables or other sensitive items where they aren’t in plain sight. Tidy-up the place so it’s presentable. Remove/correct any obvious things that are *your* responsibility, like doing dishes; making sure all non-refrigerated food is securely closed and counters, stove, and any spills are cleaned up so there’s no attraction for vermin; making sure the tops of kitchen cabinets are cleared; all your outlets are accessible; there is clearance around your heating/air conditioning unit(s); and hit your bathtub with some mold/mildew cleaner if it needs it.