Pressure and temperature do double duty in reactor work: they are the experiment's conditions and its hazards at the same time. Controlling them well serves both masters, and controlling them sloppily betrays both.
You control what you measure at the right place: vessel pressure at the vessel, not upstream of a restriction, reaction temperature in the liquid, not on the furnace skin. Under irradiation, internal temperature runs hotter than external setpoints suggest, and the gap grows with light intensity and absorbance.
Pressure ratings depend on temperature, seals weaken and materials creep as heat rises, so the operating point must be checked against the coupled rating, not the cold rating. The same applies to windows: optical elements derate with temperature, and the derating curve belongs in the operating procedure.
Baths overshoot on startup and lag on load changes; expect and pre-compensate. Pressure regulators can drift with cylinder depletion. Every control loop needs a defined failure state, power-off, vent-open, and an interlock that reaches it without human reaction time.
Pressure and temperature set the reaction's rates and equilibria, so unstable conditions mean irreproducible data even when nothing dangerous happens. Small oscillations in temperature translate to visible scatter in rate constants. Tight conditions are not perfectionism, they are the error bars on every number you report.
For pressure- and temperature-controlled photoreactor configurations, see Perfectlight's reactor line and catalysis solutions.
