If there is no longer any dry ice, then there is no hazard so I don't even begin to understand what his concern is. You might want to ask. Dry is is not like radioactivity: it turns into gas and is in the air now, so any damage that could be done, has been done. No point in closing the barn door after the cows are gone.
If there is still some dry ice, then there will still be some CO2 given off when the ice "melts" (sublimates) but the amounts involved are not going to be a hazard in an apartment or house unless there are many, many tens of pounds, and even then, I would just open a window.
The short term exposure limit for CO2, according to OSHA, is 54 grams per cubic meter of air. that is a LOT of CO2. A small room like my office has about 20 cubic meters of air (3mx3mx2m or 10 feet by 10 feet by 8 feet) so I would need a kilogram (20x 50g=1 kg) of dry ice to turn into gas to even get close to a problem, if this room was totally airtight (and it isn't).
How much dang dry ice was there in that container?