Research report on tunnel emission stacks

Tunnel Еmissiоn Stасks 8

Tunnel Еmissiоn Stасks


Emissions from the tunnels pose a health risk to not only tunnels users and personnel but also to the surrounding community (Gattinoni et al. 2014). Notably, engineers have a key role to play in order to ensure that all measures and steps have been followed to redirect harmful emissions from the tunnel, which ranges from design to maintaining of a tunnel. With increased number of tunnels across the globe, there is need to reduce the health effects of gases such as CO or NO2 to the public. The following paper seeks to provide an overview of the impacts of air pollutants to the surrounding people by briefly providing results of a survey that involved participants from a tunnel vicinity. The paper will also discuss role of engineers in preventing impacts of emissions to the community.


Evidently, in the field of road tunnels, air quality is conventionally regarded in relating to the level of vehicle exhausts’ concentrations inside a given tunnel (Gattinoni et al. 2014). However, it is important to realize that high concentrations of pollutants outside a tunnel cannot only be harmful to the people around but also to the environment. Notably, the continued accumulation of such pollutants reduce rapidly from exhaust or a portal shaft to the surrounding environment based on the complex mechanisms including the direction and the speed of the wind as well as the neighboring topography (Pang 2015). Resultantly, it is realized that the quality of the air around the vicinity or tunnel portals as well as other exhaust points attract some interest especially when there is an increase in the traffic intensity or the tunnels are constructed in a given urban environment. Admittedly, above a given tunnel, it is expected that the air quality should be better than if an open-air section of the road was situated in the same location. However, in shafts and portals, the polluted air is usually let free where a transverse and longitudinal airflow is discharged thought the piston effect of the ventilation systems and /or traffic systems. Accordingly, depending on the background of the concentration as well as any other sources that are localized and close to a given tunnel shaft or portal, the levels of the concentration of the pollutants can sometimes exceed the maximum levels set by authorities (Nordic Council of Ministers 2015). In such circumstances, measures should to be taken in order to improve the quality of the air in the surrounding community. Connectively, some of the main steps that can be taken include mechanical and civil works, planning and improving the land use in the tunnel’s vicinity, among others (Gattinoni et al. 2014). Critical to note is that in most cases, it is not possible to reduce the concentration of pollutants based on the operational measures such as changes done in the ventilation regime. At the same time, the stakeholders need to be keen in selecting the optimum location of a tunnel, gradients, type of ventilation , management of air discharge, maintenance of tunnel , management of traffic , and if useful, application of suitable removal techniques.

Results of the Survey

The survey was conducted for three years consecutively, which included 2006, 2007, and 2008 to assess the impact of air pollutants on the community. The researchers divided their studies on four categories, which were the reduced exposure zone, increased exposure zone, Eastern stack zone, and control zone. In one of the key areas of the study, the researcher had to collect demographic and symptomatic data from the participants. In 2006, the researchers conducted the study on 1024 respondents. The results indicated that under reduced exposure zone, there were increased levels of asthmatic cases in the community. For example, the researchers found that 18 community members had newly diagnosed with asthma. At the same time, it was noted that 11 community members had previously been diagnosed with asthma while the same number of people were undergoing medication. Notably, the results in 2007 and 2008 did not show significant difference under the same category. However, it is important to note that under the increased exposure zone, the researcher recorded increased case of asthmatic conditions compared to the reduced exposure zone in the three years. For example, the study showed that twenty-four people were diagnosed with asthma in 2007 compared to eighteen in 2006. On the other hand, the number of current people with asthma and those that were undergoing medication remained relatively the same for reduced and increased exposure zones. In the Eastern stack zone, the researchers recorded reduced cases of asthmatic conditions among participants in three years under investigation. Although the figures were not differing with high margins, the results showed that there was a great improvement compared to the reduced and increased exposure zones. For example, in 2007, the results indicated that nineteen people were diagnosed with asthma in the Eastern Stack zone compared to twenty-four in the increased exposure zone, which is a considerable reduction. However, under controlled exposure zone, the results indicated that there were positive developments in relation to those who showed impacts of air pollutants. For example, it was only seventeen people who were diagnosed with asthma, which is lower than any other previous categories.

Besides showing asthmatic conditions, the results also indicated that community members were inhaling corticosteroids. As noted above the levels of impacts and symptoms of the pollutants were relatively different from one category to another. The same applied to the inhaled corticosteroids. For example, in 2007, there were seven and five people who had inhaled corticosteroids under Eastern stack and controlled exposure zones respectively. At the same time, participants also showed signs of coughing, lower, severe lower, and upper respiratory symptoms. In all the respiratory symptoms depicted by the participants in three years, there were reduced occurrences in controlled exposure zones compared to the other zones. Finally, results also showed that the surrounding community was also having mouth symptoms of pollutants’ effects, which also varied depending on the categories. However, researchers noticed there were some participants who were smokers, which would explain the symptoms depicted under every category.

Further, in line with the other factors in the community, the researchers also investigated home environmental issues such as the presence of unflued gas heater. In addition, the researchers also recorded the level of education for the participants in all categories. Unlike other categories, for three years, the number of people who had up to middle school level of education was higher in control zone.


. In this way, ventilation stacks are utilized and installed to increase fresh air throughout as well as effectively increasing the acceptable vehicle capacity. In addition, stacks are also used where tunnel portals are situated in residential or urban areas specifically where ambient air quality is poor. In such cases, fans are installed to directly divert most of the tunnel air of a different stack at elevated heights instated of using portals at the ground level. In Australia, engineers have designed some tunnels so that the tunnels air is removed through the stacks which ensures there is zero exhaust emissions at the portals such as Lane Cove tunnels, Cross City , and Sydney’s M5 East. (Mckenna 2008). However, for most of the long and busy roads, emissions are able to build up and accumulate in tunnels to levels where unacceptable limits of air quality are reached (Pang 2015)In the above results, it is clear that the stacks play a critical role in redirecting tunnels emissions thus reducing their effects to the public or the surrounding community. As noted, there are different ways in which pollutants from tunnel exhaust or shafts can affect the surrounding community. At the same time, engineers have key roles to play to ensure that pollutants from tunnels are contained thus reducing the effects on the public. Accordingly, most road tunnels vent exhaust air to the atmosphere at exit portals

Engineers have the responsibility of not only coming up with designs that minimizes air pollution but also following the regulation including traffic rules. For example, tunnel engineers are required to ensure that there is enough ventilation in tunnels and that considerable percentage of emissions are directly appropriately to minimize their impacts on human health and the surrounding environment. Notably, some of the common harmful emissions from tunnels include CO and NO2, which are contained in vehicles’ exhaust gas.


Engineers have a key role to play in ensuring that all measures and steps have been followed to redirect harmful emissions from tunnels. Importantly, an engineer should take consideration of all forms of ventilation systems, which include transverse, longitudinal, semi-transverse ventilation and the combination of these three types. Together with the installation of stacks, the above health impacts of emissions can be reduced.


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Kuna-Dibbert, B. (2015). Health effects of transport-related air pollution. Geneva, World Health


Nordic Council of Ministers. (2015). Improved emission inventories of SLCP Background

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Pang, L. K. (2015). Air and noise pollution control. Clifton, N.J., Humana Press.

Mckenna, J. D. (2008). Fine particle (2.5 microns) emissions: regulations, measurement, and

control. Hoboken, N.J., John Wiley & Sons.