The present invention provides a system and a method for determining the particulate matter mass in vehicle emissions tests, seeking to improve weighing resolution and reduce experimental uncertainties. The invention presents two embodiments, in which in the first embodiment there is a branch in the vehicle emissions collection equipment that allows to integrate the particulate matter generated during the entire test into a single filter. In the second embodiment, there are two branches in which one branch has a filter for the accumulation of the particulates produced in phases 1 and 2 of the test and the other branch has another filter for the accumulation of the particulates in phases 2 and 3.

An exhaust gas analysis device analyzes exhaust gas generated when fuel is combusted. This exhaust gas analysis device includes a first analyzer that measures a concentration of a component to be measured in the exhaust gas, a second analyzer that measures a concentration of CO.sub.2 in the exhaust gas, a storage portion that stores a hydrogen/carbon ratio, which is a ratio between hydrogen and carbon composing the fuel, or an input receiving portion that receives an input of the hydrogen/carbon ratio, a moisture concentration estimating portion that, based on the measured CO.sub.2 concentration and on the hydrogen/carbon ratio of the fuel, estimates a concentration of moisture in the exhaust gas, and a correcting portion that, based on the estimated moisture concentration, corrects the measured concentration of the component to be measured.

There is provided a vehicle-mounted drain separator 100 that is used in a vehicle-mounted exhaust gas analysis device 200, and that includes an exhaust gas flow path EL through which flows exhaust gas, and a dilution gas flow path AL through which flows a gas that is taken in from the outside in order to dilute exhaust gas, and that merges with the exhaust gas flow path EL at a confluence point CP located at a downstream end portion. The vehicle-mounted drain separator 100 is formed in such a way that a heat exchange is generated at least on an upstream side of the confluence point CP between the exhaust gas flowing through the exhaust gas flow path EL and the gas flowing through the dilution gas flow path AL.

A dilution gas mixing unit that is used in an exhaust gas analysis system that analyzes the mixed gas obtained by diluting an exhaust gas with the dilution gas, and mixes the dilution gas with the exhaust gas is provided with a dilution gas supply pipe that is connected to an exhaust gas introduction pipe into which the exhaust gas is introduced and supplies the dilution gas to the exhaust gas introduction pipe, a dilution gas sampling unit that is provided in the dilution gas supply pipe and collects the dilution gas, and a backflow prevention member that is provided closer to the exhaust gas introduction pipe than the dilution gas sampling unit in the dilution gas supply pipe and prevents the mixed gas from flowing backward through the dilution gas supply pipe.

In order to allow an analyzer to be calibrated or a sampling channel to be purged without removing a sampling probe from a sampling location, provided are a sampling channel through which an exhaust gas from an internal combustion engine flows, an analyzer that is connected to the sampling channel and analyzes the exhaust gas, a diluter provided upstream of the analyzer in the sampling channel, a recirculated channel that branches from a branch point set between the analyzer and the diluter in the sampling channel and joins the diluter, a pump that is provided in the recirculated channel and guides part of the exhaust gas from the branch point to the diluter, an additional channel that is connected to the recirculated channel or the sampling channel and through which a calibration gas or a purge gas flows, and an opening and closing mechanism provided in the additional channel.