Hanuman is Amshaavataara, being descent of only Mukhyapraana, one attribute(Kala) of  Vishnu. All other avataaras are partial descents as God had descended only with one or a few Kalas at a time. Only during Krushnaavataara, God had come with all Kalas. Krushna was Poornaavataara. Madhwaachaarya also is mukhapraana manifested.

Mukhyapraana manifests as Panchapraana in us. In His presence, the five Praanas. take over the functions of inhaling, exhaling, blood circulation, overall surveillance of all functions in the body and excretion/ procreation. At the time of death if Mukhyapraana leaves earlier, a person goes into coma. When the Panchas leave, man is declared dead.

Praana is a force and science talks of it as Boson, named so after Satyendranath Bose. Boson is a particle subtler than protons and neutron and electron set And more subtler than the next set of six quarks. We know the vacuum in the  outside world on the universe. In the same scale the vacuum inside the  atom is no less amazing.

Praana is not breath. Praana is not the air we breathe. Purushasookta tells-Praanaadvaayurajaayata. Vaayu was born of Praana. Vaayu is not air either. It is the element, subtle in origin and gross in manifestation. We have lost further knowledge of their nature.

Group of five UPA-praaanas govern sneezing, coughing, belching , vomiting   and batting of eyelids and so on.

Breathing is not involuntary. When the diaphragm  relax, the flexible  lungs fall and the vacuum draws in air, science tells us. When doing sheersaasana , the flexible lungs collapse. No vacuum. Praana draws in  air.