Babies have little control over their hands and many other body parts, so their mouths are often the best way for them to explore objects. It’s extremely important for parents to watch what babies put in their mouths, especially when they become mobile and if they have older siblings.
If your older children have toys with small parts try to create a baby-free zone with a door or some other kinds of boundary where older children can play with their toys away from Baby. Also, make sure all toys are put away before the older child leaves the area.