At standard conditions, hydrogen is a gas of diatomic molecules having the formula H₂ and is the lightest element with the symbol H and atomic number 1. It is colorless, odorless, tasteless, non-toxic, and highly explosive.
Monitoring hydrogen (and nitrogen) in solar cell manufacturing is essential to quality control in polysilicon manufacturing. In-line thermal mass flow meters do not require separate temperature and pressure measurements, have fast response time, and low-pressure drop. They are essential instruments for controlling and monitoring the process of polysilicon manufacturing. Other hydrogen applications where thermal mass flow meters may be used include measuring the flow rate to hydrogen reactors in batching operations and gas distribution systems and monitoring the hydrogen flow (used to cool the turbines) to detect leaks in the plant turbine generators. Hydrogen and other gases, such as argon and helium, can also be used in heat treatment where its measurement is required.