How can nicotine inhalers work?

Why wouldn't they: Nicotine is inhaled with every cigarette someone smoke, but it comes together with carbon monoxide, formaldehyde and a host of organic "tars" which cause cancer etc. Nicotine inhalers have purified nicotine with a measured amount per spray, and work a little faster than nicotine gum or lozenges to relieve nicotine withdrawal symptoms and help people stop smoking.