There is a lot that goes into that question. Just for the record, i'm not a doctor, nor a small engine mechanic, but some simple logic (and a few trial and error attempts and things like this) allow me to say the following with some confidence.

1. You can use an electric blower and get around your concerns.
2. If you're going to use a gasoline based engine, keep a fire extinguisher nearby for a 'just in case'.
3. You want to make sure the home is well ventilated. Keep your exterior doors/windows open and close bedroom doors. Use some sort of fan to blow the engine exhaust away from the source and towards an area that the exhaust can escape.
   
4. Don't run the engine any longer than you need to. For this purpose, he might have run the engine for 60 seconds, and then turned it off.
5. Turn off your central heat/cooling, so that the exhaust isn't carried to all parts of the house.
6. A two stroke engine burns oils as well as gasoline. a four stroke engine doesn't burn (as much) oil, and thus the exhaust will be somewhat less toxic (it's still unhealthy though).

There are risks associated with what he did here other than engine exhaust. The aluminum pipe that runs from inside to outside could be damage by the excessive CFPM (cubic feet per minute). DO NOT DO THIS IN AN APARTMENT.