Air Liquide has received a draft letter of conditional approval from the FDNY to move forward on plans to build two hydrogen stations in New York City for refueling zero-emissions, fuel cell vehicles.

The projects appear to be on somewhat of a faster track than expected, as Air Liquide has already filed plans with New York’s Department of Buildings to build the stations - one at 668 3rd Ave. in Brooklyn’s Greenwood Heights neighborhood; and another at 2274 Tillotson Ave. in the Eastchester section of the Bronx.

The Paris-based gas giant is waiting to hear from the DOB about plans filed today for the Bronx station, and is currently working out conformance issues with examiners regarding plans filed in June for the Brooklyn site.

Approvals from the FDNY and the DOB are required before construction can begin. The FDNY’s draft concept letter enables Air Liquide to move forward in the process.

Local officials had initially predicted up to a two-year permitting timeline for the stations. But dates for groundbreaking at the sites appear to be closer to months away rather than years, given the stage of permitting the projects are in.

Conditions the FDNY placed on the approvals include a requirement that attendants be stationed at the dispensers to manage the refueling process for consumers. This is according to an update (at 16:25 mark in the video) given in July by Joe Gagliano, an infrastructure business development specialist at the California Fuel Cell Partnership.

Four other Northeast stations in Hartford, Conn.; Providence, R.I.; Mansfield, Mass.; and Hempstead, N.Y. on Long Island, are already under construction. All four are expected to open before yearend, but the Hartford dispenser appears the farthest along; it’s expected to open first in the fall, followed by the station in Providence.

Fuel cell electric vehicles (FCEVs) are one of the world’s two main types of zero emission vehicles (ZEVs) - automobiles which release no pollutants when they’re driven; battery electric vehicles (BEVs) are the other.

FCEVs, however, have longer ranges (over 300 miles) in lighter packages than BEVs. And although they require hydrogen to run, FCEVs can be fully refueled faster - in about five minutes - versus the hours to days it takes to completely recharge BEV batteries. Fuel cells generate electricity via a circuit through which hydrogen travels to mix with oxygen.

In the last three years in the U.S., fuel cell vehicles, including Honda’s Clarity sedan, Hyundai’s Tucson SUV and Toyota’s Mirai sedan, have been offered to the public, although thus far only in California, which has 30 retail hydrogen stations stretching from Truckee to San Juan Capistrano. Japan leads the world with 90 hydrogen retail stations opened, followed by Germany, with 32.

Carmakers are awaiting completion of multiple hydrogen stations in the New York-Boston corridor before they allow dealerships to offer fuel cell vehicles in the Northeast.

Experts consider hydrogen safer than other automotive fuels (at 3:32 mark in video). That’s because hydrogen is 14 times lighter than air. So it quickly rises and dissipates up and away from ignition sources on the ground, whereas traditional gases and their vapors pool up and around a vehicle during a leak or crash.