An example system for measuring emissions from a building includes a housing, a plurality of sensors arranged in the housing to detect concentrations of gas constituents in gas exiting the building, a gas flow sensor to detect a gas flow rate of the gas exiting the building, and a computing device to perform functions of calculating a total emissions of the particular gas constituent being tracked from a concentration of the particular gas constituent detected by the plurality of sensors and the gas flow rate, calculating an emission rate of the particular gas constituent being tracking, determining whether the total emissions and the emission rate of the particular gas constituent are within acceptable ranges, and based on the total emissions and the emission rate of the particular gas constituent being outside the acceptable ranges, outputting a prompt to a building computer system or operator indicating an alert.