As Hurricane Irma rages through Florida, people are relying on the free walkie talkie app Zello to stay connected.
The app, an alternative to texting that lets you have public and private conversations via Wi-Fi or cellular data, raked in one million new users every day since last Monday, Zello CEO Bill Morris told Recode. During that time, Zello has shot to the top of Apple's US App Store, where it is now the top free app.
Most of the app's new users are from Puerto Rico and Florida who signed up as a preparation for Hurricane Irma, according to Zello Founder and CTO Alexey Gavrilov. People have used it to coordinate group efforts to retrieve supplies, gas, and prepare their houses for the wind and rain. You can also use Zello to find and connect with local search and rescue channels, or create your own — as many in Texas have done following Hurricane Harvey.
The app does have limitations, though.
"While Zello has been helpful in Harvey relief efforts, it is not a hurricane rescue tool and is only as useful as the people who use it, and as reliable as the data network available," Gavrilov wrote in a blog post.
That means if your Wi-Fi and cellular data go down, you won't be able to use Zello (or any other communication apps, for that matter). Gavrilov said that may not be an issue because mobile data networks have historically remained "at least partly operational, even after a severe disaster."
With that being said, Zello could be particularly handy right now, since it uses just a "fraction of bandwidth of phone calls and will often work when phone calls won't get through," Gavrilov wrote.
"After a disaster, mobile networks will typically be overloaded with phone calls so don't make phone calls unless you have an emergency and need to call 911," Gavrilov wrote. "This will not only allow emergency calls to go through better, but will also extend the lifespan of mobile towers running on backup power."
Just keep in mind that Zello "will use a lot of battery" when you're actively using it, Gavrilov wrote. So, at the risk of stating the obvious, if you lose power, you'll probably want to use it sparingly. To extend battery life while using Zello, Gavrilov recommended turning your phone screen off while listening, unless you're connected to a power source. Doing so will extend the battery life of your phone by "at least 2x," he wrote. Also be sure to turn off Zello if you have less than 30 percent battery. This way you'll still get a push notification if someone sends you a message, but the app won't use any power.
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If your cell service goes down, try using a backup SIM card from a different carrier, if you have one. Or, if you can't connect using 4G, try switching to 2G or 3G and Zello might start working. Also be sure to memorize your Zello password, so you can sign in on another device and re-connect with your contacts if your phone is damaged or your battery dies.
For more information on how Zello works, head here.