Being a non-smoker myself, I often find working with smokers to be irritating for various reasons. Are there any laws prohibiting the employers from discriminating against smoker employees in their companies in either Canada or USA?
Smokers are not a federally protected class, but state rights vary. This article shows a map of which states have enacted legislation protecting smokers. I suspect with healthcare costs going nowhere but up, more and more companies will try to hire nonsmokers only.
Federal employment law doesn't protect against smoker discrimination, only prohibiting employment activities that discriminate on the basis of race, color, religion, sex, national origin, age, disability, and genetics.
States are free to protect workers from other discriminations.
Twenty-nine states and the District of Columbia currently have laws that protect workers from smoker discrimination, prohibiting employers from refusing to hire smokers and from banning them from smoking outside of the workplace.