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.
Vents admit air into the pipes that helps equalize the air pressure in the pipes to prevent blowback and siphoning of the water seal in the trap. The trap. All fixtures need one, and only one, trap that is set level. Fixtures with an internal trap, like a toilet, do not need and should not have a separate trap. One trap provides the water seal to keep out sewer gas. Two or more traps impede flow and are more likely to become clogged.