The ability to text 911 in an emergency became available Thursday in select areas. This service could prove incredibly helpful to individuals who are deaf, hard of hearing, have a speech disability or find themselves in a situation where a voice call to 911 might otherwise be dangerous or impossible.

All major U.S. wireless carriers – Verizon, AT&T, Sprint and T-Mobile – committed to launching the service by May 15, when the Federal Communications Commission (FCC) adopted the policy back in January. And while the carriers met their launch-date deadline, the service’s availability is extremely limited. The FCC has published the short list of areas where the service works, and plans to expand service by the end of the year, according to the Washington Post.

Even in areas with text-to-911 capability, the FCC recommends a voice call if at all possible.

“Even where text-to-911 is available, if you are able to make a voice call to 911, and if it is safe to do so, you should always make a voice call to 911 instead,” said the FCC in a Text-to-911 FAQ.

The FCC notes that voice calls allow the 911 operator to more quickly ask questions and obtain information from the caller, while two-way communication by text can take more time and is subject to limits on the length of text messages. Additionally, when a 911 call is made, as a opposed to a text, the dispatcher will typically receive the phone number and the approximate location of the caller automatically.