Safety Index And Control Of Nitrogen Oxides In Road Tunnel

Recent years, as the fast and continuous economic development of our country, thequality of people’s live is improving while the ownership of motor vehicle is increasinglargely and continuously. Our county has build a large amount of highways and tunnelsso that roads and tunnels becomes to be the most frequently used transport facilities bypeople. But the feature that tunnels are not easy to ventilation makes a large amount ofexhausted gas is easily to be accumulated in road tunnels. The main harmfulcomposition of exhausted gas is carbon monoxide (CO) and nitrogen oxides (NO_x).Once the concentration of vehicle emission is too high, it will be harmful to the healthof boards, passengers and maintenance men of tunnels as well as safety of traffic. Thatis why we should control the concentration of exhausted gas to a safe level.Theconcentration of CO in tunnels of our country is low so it makes little effect to people’shealth, however the harmfulness of NO_x is becoming to be more and more serious. Ourcountry is focusing more on the harmfulness of NO_x. When our country proposes the12thplanning, NO_x is included in the harmful gas which should be controlled theamount of the total emission.This paper introduces the harm of CO and NO_x in tunnels and the research of theconcentration of the gas. This paper focuses on the NO_x concentration and introducesseveral NO_x concentration detection methods in detail as well as the detectionequipment and the working principles. Based on the theoretical analysis, we test NO_xconcentration in road tunnels in Chongqing which has been operated. It reveals thedistribution law of NO_x concentration, and figures out NO_x concentration safetyindicator which can be used in our country according to the use of international roadtunnels NO_x concentration standards and formula and the actual situation in our country.It also gives some suggestion in the control of NO_x concentration.The certainty of the safety range of NO_x concentration will contribute to thepromotion of ventilation design of tunnels. The owner companies can learn from thisindicator to control the NO_x concentration in tunnels which have been operated already.Meanwhile it can provide suggestions to construction and design companies. Moreoverit will provide reference to formulate the standard of the road tunnel NO_x concentration.