A gas sensor (400A-400N) for detecting target gas and test gas, comprising: a housing defining an opening to an external environment; a sensing electrode disposed in the housing and configured to generate a test gas signal when the sensing electrode is in contact with a test gas; a membrane disposed in the housing between the sensing electrode and the opening in the housing , wherein the membrane is at least partially exposed to the external environment; a test gas diffusion path defined in the housing for the test gas to travel in the gas sensor (400A-400N) and comprising an inlet and an outlet ; and a capillary disposed between the sensing electrode and the outlet of the test gas diffusion path , wherein the test gas diffusion path is disposed between the membrane and the capillary , the test gas diffusion path including a first wall and a second wall that define the test gas diffusion path , the first wall defining a first test gas diffusion path opening to expose the test gas to the membrane , the second wall defining a second test gas diffusion path opening to expose the test gas to the capillary and sensing electrode , the first test gas diffusion path opening disposed prior to the second test gas diffusion path opening along the test gas diffusion path in a direction of flow from the inlet of the test gas diffusion path to the outlet of the test gas diffusion path , such that when the test gas travels through the test gas diffusion path from the inlet to the outlet , the test gas comes in contact with the membrane prior to coming in contact with the capillary and then the sensing electrode , wherein a total amount of the test gas signal is higher when the membrane has a high degree of restriction of gas access compared to the total amount of the test gas signal when the membrane has a low degree of restriction of gas access, and wherein a magnitude of the test gas signal indicates a degree of restriction of gas access by the capillary . a housing defining an opening to an external environment; a sensing electrode disposed in the housing and configured to generate a test gas signal when the sensing electrode is in contact with a test gas; a membrane disposed in the housing between the sensing electrode and the opening in the housing , wherein the membrane is at least partially exposed to the external environment; a test gas diffusion path defined in the housing for the test gas to travel in the gas sensor (400A-400N) and comprising an inlet and an outlet ; and a capillary disposed between the sensing electrode and the outlet of the test gas diffusion path , wherein the test gas diffusion path is disposed between the membrane and the capillary , the test gas diffusion path including a first wall and a second wall that define the test gas diffusion path , the first wall defining a first test gas diffusion path opening to expose the test gas to the membrane , the second wall defining a second test gas diffusion path opening to expose the test gas to the capillary and sensing electrode , the first test gas diffusion path opening disposed prior to the second test gas diffusion path opening along the test gas diffusion path in a direction of flow from the inlet of the test gas diffusion path to the outlet of the test gas diffusion path , such that when the test gas travels through the test gas diffusion path from the inlet to the outlet , the test gas comes in contact with the membrane prior to coming in contact with the capillary and then the sensing electrode , wherein a total amount of the test gas signal is higher when the membrane has a high degree of restriction of gas access compared to the total amount of the test gas signal when the membrane has a low degree of restriction of gas access, and wherein a magnitude of the test gas signal indicates a degree of restriction of gas access by the capillary . <EOS>