text: In a typical TAP pulse-response experiment, very small (~10 mol) and narrow (~100 μs) gas pulses are introduced into the evacuated (~10 torr) microreactor
  containing a catalytic sample. While the injected gas molecules traverse the microreactor packing through the interstitial voids,
  they encounter the catalyst on which they may undergo chemical transformations. Unconverted and newly formed gas molecules eventually
  reach the reactor's outlet and escape into an adjacent vacuum chamber, where they are detected with millisecond time resolution
  by the QMS. The exit-flow rates of reactants, products and inert molecules recorded by the QMS are then
  used to quantify catalytic properties and deduce reaction mechanisms. The same TAP instrument can
  typically accommodate other types of kinetic measurements, including atmospheric pressure flow experiments (10 Pa), 
  Temperature-Programmed Desorption (TPD), and Steady-State Isotopic Transient Kinetic Analysis (SSITKA).