Within the Red Hat certification program, the RHCA is considered the most complete (and grueling) certification among the seven major Red Hat certifications. In fact, some equate the prestige of the RHCA to that of the Microsoft Certified Master and possibly the CCIE.
A plumbing fixture like a sink can not function properly without a sink vent. When a drain pipe drains it creates a negative pressure in the sink drain; the negative pressure will pull the water out of the p-trap of the sink that's draining and sewer gases can enter your home if a sink vent is not installed.
Adequate ventilation, especially if the microwave is built into a wall of cabinetry, is a must. The manufacturer's instructions will tell you how much cabinet depth you need to have for a built-in, says Sam Cipiti, vice-president of R.M. Tunis Kitchens and Baths in Chevy Chase, Maryland.