Increase the vent to 4" as hoar frost will not over lap a 4"opening
Plumbing drain vents equalize the pressure in drain piping in order to preserve trap seals on plumbing fixtures. Blocked or improperly sized vents can cause traps to dry allowing sewer gases to enter the building.
The purpose of plumbing vents in a building's drainage system is to allow air to enter the pipes, preventing suction and ensuring proper drainage flow.
One that vents one fixture
Plumbing top-out is the stage of plumbing that occurs when a home is in its frame stage. There are three stages of plumbing typically in construction. Plumbing rough (prior to the foundation being poured); plumbing topout (bringing ground plumbing up through the vents); plumbing trim (installing fixtures).
Plumbing vents work by allowing sewer gases to escape outside the house through a pipe that extends above the roof. This creates a pressure balance in the plumbing system, preventing the gases from entering the house through drains or fixtures.
Strange question I must admit, "vents" are based on the fixture units connected to it and the developed length.The local codes will also have some input on proper vent sizing as certain areas do require a 4" vent terminal to be 4" diameter to prevent hoar frost and then the Fresh air inlet part of the "Plumbing vent" system would be half the diameter of the building house drain but in no case less then 3" which ever is larger
Vents should be on the highest point of the stack and preferably on the wall outside and not in ducts, this due to future maintenance and ease of installation.
House vents are typically located both inside and outside the house. Inside the house, vents are usually found in ceilings, walls, or floors to allow air to circulate. Outside the house, vents are often located on the roof or walls to allow for proper ventilation.
Ask This Old House - 2002 Concealing Retaining Walls Quieting PVC Plumbing Vents 8-12 was released on: USA: December 2009
Return air vents in a typical HVAC system are usually located on the walls or ceilings of a room, allowing air to flow back into the system for heating or cooling.
To create an accurate bathroom plumbing diagram, you will need measurements of the room's dimensions, the location of existing plumbing fixtures such as sinks, toilets, and showers, as well as the placement of pipes, vents, and drains.
Plumbing venting rules ensure proper installation and maintenance by allowing air to enter the plumbing system to prevent suction and odors. Vents should be installed vertically, extend above the roof, and be a certain distance from windows and doors. Regular inspection and cleaning of vents are necessary to prevent blockages and maintain proper functioning.