INDIANAPOLIS (WISH) — About 1.3 billion holiday cards are sent each year in the United States, but this card is unlike any other.

“It’s like trash, egg,” said Artiest Cannady, who sniffed the card for the first time.

Others described it as “old,” “stale” and “stinky.”

Scented scratch-and-sniff holiday cards are being sent out to Central Indiana residents this month and mid-January to educate them on gas leaks.

Each card will be scented with mercaptan, an additive added to natural gas lines. Natural gas is odorless and the additive makes it easy to detect a gas leak.

The cards stink, but Citizens Energy Group is sending them out for their customers’ safety.

Ben Easley of Citizen Energy Group said, “As temperatures get colder, this is the time to talk about home heating season safety and this is part of that. Making sure if you use natural gas equipped appliances that you can detect if there’s a leak.”

“This is not to say that there are widespread leaks in our distribution system, but rather so many use natural gas equipped appliances that it makes sense for us to do this public education,” Easley said.

Natural gas leaks can cause asphyxiation and explosions, and Indiana is one of the top 10 gas-consuming states.

If a gas leak is detected, Easley recommends people move away from the area and call Citizens Energy Group or 911. As an additional safety measure, do not re-enter the area until authorities say it’s safe.

Additional gas leak safety tips are available online.