Texas outlaws the gas chamber for shelter pets.

A new Texas law makes it illegal to euthanize an animal with carbon monoxide at an animal shelter.

Lethal injection of sodium pentobarbital is now the only legal way to put down a stray dog or cat.

The old gas chambers that were used for killing animals will be mothballed.

This is the biggest legal change to affect shelter animals since the Texas Euthanasia Act that banned shelter employees from shooting, strangling, clubbing or drowning animals a decade ago.

Josh Havens, a spokesman from the Governor’s office said: the law will “put to an end a method of animal euthanasia that is recognized as cruel, expensive and unsafe. By signing the bill into law, Governor Perry was proud to add Texas to a growing list of states that outlaw gas chamber euthanasia for shelter dogs and cats.”

According to the Humane Society of the United States’ website, local shelters establish their own rules, policies and governance.

An estimated 3 to 4 million animals are euthanized at shelters in the US every year.