Section 54(3)(f) in Tamil Nadu Combined Development and Building Rules, 2019
(f)Every septic tank shall be provided with ventilating pipe of at least 5cm diameter. The top of the pipe shall be provided with a suitable cage of mosquito-proof wire mesh. The ventilating pipe shall extend to a height which would cause no smell nuisance to any building in the area. Generally, the ventilating pipe may extend to a height of about 2m, when the septic tank is at least 15m away from the nearest building and to a height of 2m above the top of the building when it is located closer than 15m.