Arizona's largest utility is encouraging those celebrating Valentine's Day with big balloons to keep them on a tight string to avoid power outages.

Mylar balloons, sold everywhere but in increasing numbers for holidays, can become entangled in power lines if released and cause localized blackouts, accourding to Arizona Public Service Co.

Last year, balloons caused 75 power outages in APS service territory, which includes much of the Valley. Those outages impacted more than 56,000 customers.

While most balloon-related outages take place between Valentine’s Day and graduation season, one balloon this year already caused an outage that lasted 13 hours.

The reason for the outages is that the metallic coating on Mylar balloons conducts electricity and can cause a short circuit or power surge that can lead to large-scale outages, melting of electrical wires, fires, property damage and even injuries to wildlife, pets and people.

APS offers the following tips to have the balloons safely:

Only use balloons indoors and away from overhead power lines. Even non-metallic balloons can become entangled in lines and cause an outage.

Always attach a weight to metallic balloons or keep them tethered at all times. 

Never play with balloons, kites or drones around overhead power lines.

Always deflate balloons and dispose of them properly when no longer in use.

Always assume power lines are energized. Keep yourself, your equipment and all other items at least 100 feet away from power lines.