A method and system for supplying an ultra-pure fluid to a substrate process chamber using point-of-use filtration and purification. The method and system provide ability to automatically monitor and control contamination levels in fluids in real time and to stop substrate processing when contamination levels exceed predetermined thresholds. In one aspect, the invention is a system comprising: a fluid supply line adapted to supply a fluid to the process chamber; filtration means operably coupled to the fluid supply line for removing positively and negatively charged particles from the fluid prior to the fluid passing into the process chamber; a purifier operably coupled to the fluid supply line in series with the filtration means for removing ionic contaminants from the fluid prior to the fluid passing into the process chamber; sensor means for repetitively measuring particle and ionic impurity levels in the fluid that has passed through the filtration means and the purifier, the sensor means producing signals indicative of the measured particle and ionic impurity levels; a controller electrically coupled to the sensor means for receiving the signals created by the sensor means, the controller adapted to respectively compare the measured particle level and the measured ionic impurity level indicated by the signals to a predetermined particle threshold and a predetermined ionic impurity threshold, wherein upon the controller determining that either the measured particle level is above the predetermined particle threshold and/or that the measured ionic impurity level is above the predetermined ionic impurity threshold, the controller further adapted to (1) activate means to alert a user, (2) cease processing of substrates in the process chamber, and/or (3) prohibit processing of substrates in the process chamber.