An environmental control system for an aircraft, comprising: a primary heat exchanger; a secondary heat exchanger; and an air cycle machine including: a compressor fluidly coupled to an outlet of the primary heat exchanger and an inlet of the secondary heat exchanger; a dehumidification system arranged in fluid communication with the outlet of the secondary heat exchanger; a first turbine fluidly coupled to an outlet of the secondary heat exchanger; a second turbine disposed downstream of the first turbine that receives air from the first turbine in a normal mode and wherein the second turbine receives the air via a second turbine inlet; and a first humidity sensor including an inlet and an exhaust, the first humidity sensor disposed fluidly between the first turbine and the second turbine that measures humidity of air that has left the first turbine as it enters the second turbine in the normal mode, and wherein the inlet of the first humidity sensor is connected to the second turbine inlet such that air is directed from the second turbine inlet through the first humidity sensor to the exhaust of the first humidity sensor, or a first humidity sensor disposed fluidly between second heat exchanger and the first turbine that measures humidity of air as it enters the first turbine in the normal mode; and wherein the exhaust includes an exhaust orifice disposed therein that is configured to control a rate of flow through the first humidity sensor. a primary heat exchanger; a secondary heat exchanger; and an air cycle machine including: a compressor fluidly coupled to an outlet of the primary heat exchanger and an inlet of the secondary heat exchanger; a dehumidification system arranged in fluid communication with the outlet of the secondary heat exchanger; a first turbine fluidly coupled to an outlet of the secondary heat exchanger; a second turbine disposed downstream of the first turbine that receives air from the first turbine in a normal mode and wherein the second turbine receives the air via a second turbine inlet; and a first humidity sensor including an inlet and an exhaust, the first humidity sensor disposed fluidly between the first turbine and the second turbine that measures humidity of air that has left the first turbine as it enters the second turbine in the normal mode, and wherein the inlet of the first humidity sensor is connected to the second turbine inlet such that air is directed from the second turbine inlet through the first humidity sensor to the exhaust of the first humidity sensor, or a first humidity sensor disposed fluidly between second heat exchanger and the first turbine that measures humidity of air as it enters the first turbine in the normal mode; and wherein the exhaust includes an exhaust orifice disposed therein that is configured to control a rate of flow through the first humidity sensor. a compressor fluidly coupled to an outlet of the primary heat exchanger and an inlet of the secondary heat exchanger; a dehumidification system arranged in fluid communication with the outlet of the secondary heat exchanger; a first turbine fluidly coupled to an outlet of the secondary heat exchanger; a second turbine disposed downstream of the first turbine that receives air from the first turbine in a normal mode and wherein the second turbine receives the air via a second turbine inlet; and a first humidity sensor including an inlet and an exhaust, the first humidity sensor disposed fluidly between the first turbine and the second turbine that measures humidity of air that has left the first turbine as it enters the second turbine in the normal mode, and wherein the inlet of the first humidity sensor is connected to the second turbine inlet such that air is directed from the second turbine inlet through the first humidity sensor to the exhaust of the first humidity sensor, or a first humidity sensor disposed fluidly between second heat exchanger and the first turbine that measures humidity of air as it enters the first turbine in the normal mode; and wherein the exhaust includes an exhaust orifice disposed therein that is configured to control a rate of flow through the first humidity sensor.