the vent openings 165 170 may not be desirable fig5 is largely similar to fig4 so like reference numbers may be assumed to be the same as described with reference to fig4 fig5 differs from fig4 in two ways first angled wall 180 a forms a smaller angle with central axis 185 for example the angled wall 180 a may form an acute angle that may be 30 u00b0 15 u00b0 or less with the central axis 185 as illustrated the angle is about 10 u00b0 second a water trap 205 is illustrated in fluid communication between the first chamber 155 and the second chamber 195 alternatively the water trap 205 may be considered a lowest portion of the first chamber 155 viewed another way the water trap 205 may be considered to have an inlet an intermediate flow passage and an outlet downstream of the first chamber 155 the water trap 205 may act as a seal that prevent steam from exiting through the vent openings 165 170 when water flows in through the water inlet device 100 a predetermined amount of water remains in the water trap 205 the predetermined amount of water is defined based upon a volume of the water trap that is below a lowest point of the outlet 125 when water is trapped in this manner the water in the water trap 205 is able to resist pressure generated in the treatment container 15 and prevent.