In Civil engineering, Is there a limit in length for a road tunnel to require ventilation?

The objectives of ventilation for road tunnels are, to dilute the carbon monoxide concentration to accepted levels for the traveling public, to effectively and efficiently manage the smoke and heat during a fire inside a tunnel. The design of a ventilation must consider in addition to length, elevation, grades, width, traffic volume, uni or bi-directional traffic, are pedestrians allowed, and fire conditions.

The problem of ventilation for road tunnels short or long is a complex issue with several variables. The objectives of ventilation for road tunnels are, to dilute the carbon monoxide concentration to accepted levels for the traveling public, to effectively and efficiently manage the smoke and heat during a fire inside a tunnel. The design of a ventilation must consider in addition to length, elevation, grades, width, traffic volume, uni or bi-directional traffic, are pedestrians allowed, and fire conditions. It is suggested that you review the ventilation chapter in the Tunneling Handbook and the National Standard502 National Fire Association for information on how to design your ventilation system, but keep in mind that your design must be approved by the authority having jurisdiction in your country.

Under road tunnel need ventilation, to normalized the carbon monoxide, but it only depend the designed and length.

Ventilation is so important in the road tunnels but I don't know if there is really a limit.

I would love to know if there is.