What are common procedures for lab absorption spectroscopy of gases?
Non-dispersive infrared absorption spectroscopy is commonly used to measure $\ce{CO}$ and $\ce{CO2}$ (and other gases, like methane and $\ce{NO2}$). The absorption overlap from water interferes with $\ce{CO2}$ measurements in particular but various algorithms can be used to mitigate this.  

$\ce{NO2}$ is more commonly measured by chemiluminescence because of its high sensitivity, but FTIR and other techniques are used for higher levels (i.e. exhaust pipe and stack emissions).