5% Acetic Acid - Vinegar - is quite safe. At worst it is a respiratory irritant. Pure acetic acid is another story - it will burn the skin badly and could easily kill someone if they drank it. If you get your vinegar in the grocery, you're good to go. If you're going to be around it frequently, you might consider wearing a respirator rated for acid-gases. This to lower the possibility of your having an asthmatic reaction around a salad-bar.