Spray Collar

Has anyone used a spray collar on a Chihuahua or a small dog that barks constantly when you leave.?
My chihuahua was crying constantly for hours when I leave the house. I have put him in a room by itself and when placed against the wall to mourn hit me pots and pans together, but he continues to mourn. I feel bad and thought of a shock collar I do not think I could do that so read up on a spray collar, seems a little nicer and ill can live with myself. Has anyone used a necklace like this or have any ingenious idea to stop smoking. He also is not recommended 6 pounds in the description neck that is about 4.7 kilos and I wondered if it still safe to use on him.
I think it's a great idea, I used one for my westie 18 pounds, and worked. That has not hurt or harm her and it worked! At first she acted as if it was just a necklace, my westie dosnt like being alone in a room, so when I go out and get out, barking. I went back and looked at me. After the first boat, spray a little mist and she kind of sneeze, and then looked at me and stopped barking, it was a miracle. She learned to stop barking and I sleep better at night without barking. Unfortanatly that broke, but it worked for about 2 months. But anyway I still think its somthing must try. It is a great alternative to a shock collar.
Belle and the Spray Collar