Microwave plasma‐enhanced chemical vapor deposition (MWPECVD) is widely used for the growth of synthetic doped diamond for electronic and electrochemical applications. Recent results have shown the possible enhancement of phosphorus incorporation using the pulsed gas injection growth method. It is therefore important to understand the dynamics of precursor gases to optimize the dopants incorporation in diamond. In this work, the dynamic response of different gases (N₂, CH₄, and O₂) impulses in hydrogen plasma is studied in two different MWPECVD reactors: a lab made NIRIM type reactor, and a commercial reactor made by Seki Diamond Systems. These reactors of different volumes are operated at different pressure and total gas flow. The time responses to the precursor gas injection are recorded by optical emission spectroscopy. Experimental time responses are fitted using an impulse response equation. Fitting parameters are extracted and compared for the different reactors, gases, total gas flow, and pressure conditions. The time responses of the different reactors are discussed as a function of their volume and the operating conditions.