Ashland, MA – BOSTON — A family pet may have helped alert an Ashland family to a carbon monoxide leak in their home, which sent four people to the hospital Tuesday.

NewsCenter 5’s Jack Harper reported that four members of the Carlton family were transported from their home at 46 Carriage House Path to MetroWest Medical Center at about 7 a.m.

The victims were conscious when EMTs arrived. The family dog, Lucky, was taken to Ashland Animal Hospital.

“Reporting that his entire family had awoke feeling ill, headaches, dizzy, nauseous, and that their family pet was unable to stand up and move around,” Ashland Fire Department Chief William Kee said.

The father, Barryn Carlton, was able to call 911.

“I’m not feeling well. My whole family is feeling lightheaded, and the dog is even acting, falling down. It’s kind of odd that all of us are not feeling well,” he said.

When Lucky collapsed, his owner knew it was not a case of the flu.

“If she has carbon monoxide poisoning, it’s a very mild case. She is doing great. She should have a full recovery,” Ashland Animal Hospital Dr. Geoffrey Kardon said.

“Dizziness, headache, nausea, and I think that the key was the family pet being unable to get up and move around. We were lucky. It very definitely could have been a tragedy,” Kee said.

All four family members were released from the hospital Tuesday afternoon.

“The dog was the one who saved us. The dog couldn’t stand. The dog was falling over, that’s when I said it had to be carbon monoxide,” Barryn Carlton said.

“I was getting ready for school, and I went downstairs and I was feeling lightheaded and dizzy, like I was going to pass out,” son Graeme Carlton said.

A faulty furnace may be to blame for the carbon monoxide leak, but the incident remained under investigation. Barryn Carlton said that his home had a working carbon monoxide detector, but the batteries may not have been working.

Last month, Gov. Mitt Romney signed Nicole’s Law, which will require every residence to have a working detector when the ownership of a home is transferred.

The law is named after Nicole Garafolo, a 7-year-old Plymouth, Mass., girl who died when heavy snow covered up a heating vent outside the family’s home, forcing carbon monoxide into the house.