International Travel – Is volunteering allowed in the United States during a visit with a B1 visa?

I am a Chinese citizen, I come from China to visit the United States. Because some of my friends can not travel with me all the time, I would like to find volunteer work while they are busy. So I wonder if I can volunteer in animal shelters, local libraries, art museums or the Red Cross.

Please tell me what I can / can not do during my stay in the United States.

I do not know where to find these rules, if you could provide them, it would be a big help.

Thank you!!