Thermo Scientific Vacuum Ovens have a radiant warm wall heating system that provides optimal uniformity and conserves chamber space for drying, curing, vacuum embedding, and plating applications. Vacuum level displayed on gauges from 0 to 30" Hg. 3" (7.6 cm) glass wool insulation prevents heat loss from working chamber. O4390-1 thru -5E Vacuum Ovens feature a hydraulic thermostat to control temperature to ¬±1.5°C with a uniformity of ¬±5°C (@ 100°C; 25" Hg) and built-in overtemperature protection. O4390-6/6E Vacuum Ovens feature programmable microprocessor-based P.I.D. temperature control that regulates to within ¬±0.2°C with a uniformity of ¬± 2.4°C (@ 100°C; 25" Hg). The programmable microprocessor-based temperature controls on O4390-6/6E Vacuum Ovens run at a single set point or utilize a 24-step program of ramps and dwells. These vacuum ovens feature independent vacuum and purge needle valves. Silicone door gasket and positive latch door maintain seal at all vacuum levels. Exclusive polycarbonate safety shield protects door glass. O4390-1/1E have top-mounted independent evacuation and venting vacuum fittings; all other models feature front-mounted three-way valve for evacuation, venting, and purging of inert gases (e.g. Nitrogen or Argon) with vacuum fittings on front of unit. Vacuum fittings require .25" (.6 cm) I.D. tubing. O4390-6/6E has 0.25 compression fittings on the left side and requires 0.25 O.D. copper or stainless steel tubing. Easy-to-clean #304 stainless steel chamber interior. Powder coated heavy gauge steel exterior construction. Vacuum and air lines constructed with corrosion-resistant stainless steel tubing for optimum chamber cleanliness and long-term performance. Two removable stacking aluminum shelves included standard.