Since the 2010 census, Houston has become one of the 20 fastest growing metropolitan areas in the nation, calling for a demand of new mobile and home numbers within a limited pool.

According to the Public Utilities Commission there are only 100 prefixes—three digit numbers for local exchange—left within the existing area codes. In mid-May, the North American Numbering Plan Administration introduced area code 346 to be implemented September 30, 2014 to accommodate the continued growth in and around Houston.

The 346 area code will overlay Harris, Waller, Austin, Montgomery, San Jacinto, Liberty, Chambers, Fort Bend, Galveston and Brazoria counties with the existing 713, 281, 832 home and mobile area codes.

All new mobile and home numbers within the region affected will receive the new 346 area code, which will generate 7.9 million available phone numbers.

Fort Bend and Montgomery counties have experienced the highest level of growth with a nearly six and seven percent population increase since April 2010, respectively. Since 2010, Harris County has seen a population increase of about four percent resulting in new neighborhoods and businesses within the Cypress area.

Although the new area code will accommodate population growth, rapid evolving areas will necessarily not be assigned numbers with a 346 area code.

"It has to be scheduled, all the programming has to be done on a coordinated businesses," said Terry Hadley, spokesman for the PUC. "Even if you're in the slowest growing region—it doesn't matter what region you're in—you could receive a new area code."

Since 1996, the Houston-Metro area has experienced two area code additions with 281 in 1996 and 832 in 1999 after 713 was introduced in 1947. Hadley said the small scope the area codes were added were not to track steady population growth—roughly 2,000,000 people between 1990 and 2000, according to the U.S. Census Bureau—but with the expansion of economic growth and the introduction of new businesses, the addition of 346 will accommodate businesses accounting for more than one phone line.

"As new businesses open up, they need a new phone number and it makes a multiplier effect," Hadley said. "Sometimes you need more than one number per customer. Now we're at the point where businesses will issue a mobile phone for employees."

The new area code will not require reprogramming changes to existing equipment because of the already existing 10-digit dialing for local calls in the affected regions.

Beginning summer 2013, the PUC will provide industry preparation and customer education information concerning the inclusion of the 346 area code.