Like so many entrepreneurs who have opened vaping shops lately, Stephen D’Angelo was a heavy smoker who finally kicked nicotine after switching to electronic cigarettes, which he viewed as a healthier — and less smelly — alternative.

Mr. D’Angelo runs a 500-square-foot store on a suburban corner in Hartsdale, N.Y., and, after seven months in business, has just started to turn a profit. But now his future — and those of thousands of other vaping entrepreneurs who have gotten into the business recently — is cloudy, since new Food and Drug Administration regulations seem poised to clamp down on e-cigarettes for health reasons.

The regulations, which the agency imposed in August 2016 and are set to go into full effect in August 2018, require costly testing of all vaping products, and offer new guidelines on manufacturing, sales, packaging and advertising of e-cigarettes. The agency said it would begin to review the health risks of all e-cigarettes introduced since early 2007, and potentially ban products it deemed harmful.

Some people anticipate that President Trump, with his oft-stated pro-business stance, will slow the regulations or stop them from going into effect. But that is small comfort to those whose livelihoods depend on e-cigarettes and who credit vaping with turning their lives around.