Tunnel Sensors - Frequently Asked Questions
Why do tunnel operators monitor air quality in road tunnels?
How harmful are the pollutants in road tunnels?
Why do we measure airflow and direction in road tunnels?
Why should I buy from Tunnel Sensors?
What is different about Tunnel Sensors Technology?
Your NOVICOM sensors calculate NO2/NOx from NO, rather than measure it. Is that valid?
What is the most important element of any tunnel sensor?
Why do tunnel operators monitor air quality in road tunnels?
Motor vehicles produce Carbon Monoxide, Nitric Oxide, Nitrogen Dioxide and fine particulate as part of their combustion process. Pollution sensors are used to operate ventilation systems that clear pollutants from the tunnel and prevent a build up of harmful substances.
How harmful are the pollutants in road tunnels?
Carbon monoxide is mostly unpleasant but at levels above 100 ppm it is harmful and at 4000ppm it is fatal. Tunnel operators try to keep levels below 30ppm. Nitric Oxide is mildly toxic but Nitrogen Dioxide is extremely toxic, levels of 60ppm are harmful and 150ppm is fatal. Tunnel operators like to keep it below 1ppm. Fine dust particles (less than 10 micron in diameter) adhere to the lining of the lung and can cause respiratory infections and possibly cancer. Large amounts of particulate also impair a drivers ability to see long distances.
Why do we measure airflow and direction in road tunnels?
The tunnel operator needs to know that there is a steady flow of air through the tunnel to clear pollutants. An Airflow monitor also indicates the direction of airflow and the velocity of the air; this is important as high wind speeds are a danger to motorcyclists. The airflow monitor is an important weapon in the event of a tunnel fire as it can be used to control the amount of air to the fire.
Why should I buy from Tunnel Sensors?
Tunnel Sensors was formed specifically to serve the tunnel industry and has designed all its sensors specifically for the unique tunnel environment. All our competitors are companies that primarily service the stack monitoring industry (gas emissions from industrial combustion processes) and the tunnel sector is therefore secondary to them. Their tunnel instruments are usually variants of their stack monitors adapted for the tunnel, which is clearly not ideal. Our employees have many years of tunnel monitoring experience between them and we use that experience to provide great product with great service.
What is different about Tunnel Sensors Technology?
Our sensors are fresh designs based on established principles. We’ve taken tried and tested measurement principles but used the latest materials and technologies to produce designs which get much better results from the same established techniques. The majority of our competitors have instruments that were designed during the cold war, and despite the nostalgic philosophy of “if it ain’t broke, don’t fix it”, there is no denying that technology has improved, both in performance and in reliability, since the conception of those old designs. Our sensors take full advantage of new technology.
Your NOVICOM sensors calculate NO2/NOx from NO, rather than measure it. Is that valid?
The direct measurement of NO2 in road tunnels is fraught with difficulty and is very costly. Indeed the World Road Association states,” NO2 cannot be measured reliably by industrial devices” and, “There are many laboratory devices enabling to measurement of NO2 precisely. However, the complexity, the cost and environment needed for this type of device do not allow their systematic use in the ventilation control system.”
The World Road Association also state that estimating NO2 to be 10% of the NO concentration is a very good indication. This has been backed up by long term trials in a road tunnel in the north of England which found the ratio to be about 11:1. We feel that making an accurate NO measurement and calculating NO2 to be approximately 10 % of that is highly relevant.
What is the most important element of any tunnel sensor?
Reliability. Unreliable tunnel sensors cause a great deal of trouble and expense, especially when the tunnel has to be closed down to effect repairs. This is why Tunnel Sensors have gone to enormous trouble to ensure our products require minimal maintenance and can be repaired in-situ.
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