Ultra-high purity (UHP) zero grade nitrogen generator transforms standard compressed air into 99.9999% nitrogen, exceeding the specification of UHP cylinder gas. The units can produce up to 1.1 lpm of UHP nitrogen gas and up to 2.0 lpm of research-grade purity nitrogen gas. A catalyst module is incorporated in the generator to oxidize hydrocarbons from the inlet air supply. Applications include GC carrier and make-up gas and low flow sample concentrators.