I don't think you'll find any totally non-smoking hotels in Paris. Maybe smoking in public areas at some hotels is prohibited but there is always a large pourcentage of rooms allocated to smokers.
Most Best Western in Paris are nice and have been renovated and like elsewhere have to respect fire regulations. If you refer at some fires that happened last year in hotels, I wouln't be anxious about that. BW Hotels are not is the same category than those low-cost hotels which are basically long term residence for "homeless". In fact, most BW Hotels in Paris are much nicer than the majority of North American BW properties.