The city announced a new e-bike incentive program last Monday to give discount vouchers to eligible residents who want to buy an e-bike for personal use. E-bikes, however, can pose a serious safety risk because if the battery catches fire, it cannot be extinguished.

E-bikes and other electric vehicles are generally powered by rechargeable lithiumion batteries, which can ignite if they are stored incorrectly, charged improperly, or simply not up to industry safety standards.

“It’s not like these things are igniting everywhere, but when they do, the problem is that we can’t really put them out,” said Milosh Puchovsky, a professor of fire protection engineering at Worcester Polytechnic Institute who studies lithium-ion batteries. “This type of fire is just more energetic. It’s more explosive, or it can be.”

The mayor’s office said in a press release that bikes eligible for the incentive program would have a safety certified rechargeable battery. The Boston Bikes website specifies that a standard e-bike battery should supply 750 watts or less of power and should meet at least one of two industry safety standards with a one-year warranty.

However, Puchovsky noted, e-bike batteries eventually do need to be replaced from normal wear and tear. If the city does not cover replacement batteries in the future, he said, participants in the program may opt for cheaper batteries that do not meet the industry safety standard.

“The battery from the original manufacturer may have a more robust safety mechanism,” Puchovsky said. “It may have UL [industry safety] standards. But if you go online, you can get a battery that fits what you’re looking for, by a third party, and it’s a lot cheaper. Why is it a lot cheaper? It may not have the same safety mechanisms. What Boston is suggesting, it’s for certain income levels, and so that’s going to be a barrier already.”

To qualify for the program, residents must either earn less than 40 percent of Boston’s area median income, be over 60 years old, or have a permanent or chronic disability.

Another important factor in mitigating the fire risk is determining where and how participants will charge their e-bikes. The Boston Bikes web page does not mention how residents are expected to charge their bikes. “If they’re bringing them into their homes and charging them, keeping them charged overnight, constantly charging them, that just increases the risk,” Puchovsky said.

Boston Bikes did not respond to a request for comment.

The city plans to provide around 1,000 e-bike vouchers ranging from $800 to $2,400 to a randomly selected group of qualified applicants. The mayor’s office said in a press release that the goal of the program was to improve historic inequities in transportation access and encourage more environmentally sustainable modes of transportation.

The first application round ends on August 24, and the city will host events for residents to try an e-bike before the period closes. The program also has a rolling application for powered handcycle wheelchair attachments, which closes on September 5.