Is using IQOS risk-free?

No.  IQOS and HEETS are not  risk-free. They deliver nicotine, which is addictive.
If you are concerned about the health effects of smoking, your best option is to quit tobacco and nicotine use altogether.

CHOKING HAZARD — IQOS accessories and HEETS tobacco sticks contain small parts.
INGESTION HAZARD — If a HEETS tobacco stick is swallowed, seek medical attention immediately due to risk of nicotine intoxication.

IQOS is the first and only tobacco heating system authorized by the US FDA as a Modified Risk Tobacco Product.*

*This does not mean that IQOS is risk-free or that the FDA has approved or endorsed IQOS.