Calibration Ammonia Sensor and Gas Concentration My name is Felipe and this is my first post here.
I'm working on a project to calibrate an electrochemical ammonia sensor. But I have a lot of doubts because I am a layman in chemistry. I'll list them and I'd be grateful if you could respond them.

The system I have here is basically a cylinder with ammonia gas of known concentration connected by a 0.5 lpm regulator and a tygon tube to a chamber where the sensor is.
Here are my doubts:


When I open the regulator the gas starts to flow into the chamber, the concentration of oxygen(or other gases) in the chamber can affect the concentration of ammonia gas? Or even if the gases mix, there is a fixed concentration of ammonia?
I've seen a lot of calibration videos. Why does nobody care about the tube length? I think as long as the tube length more is the waste of gas, right?
When I stop with the ammonia gas flow and disconnect the tube from the chamber. What are the precautions I should take with the contaminating ammonia in the air? Let's say I'm using a calibration gas of 50ppm
The calibration gas will purge the air out of your chamber, so that it contains 50 ppm NH3.  This assumes that there are no reactions that change the mixing ratio of the ammonia (e.g. reaction with water in your chamber).  The length of the tube doesn't matter unless the gas reacts with your tubing, though length will decrease the pressure of the gas coming out of the tube.