IF YOU LIVE near a Caltex petrol station you may increasingly have noticed taxis pulling up to have that oval-shaped particulate filter on their exhausts removed and cleaned. They should be doing it every two days and public light buses (PLB) every day.
At least they should be if they are following the guidelines laid down by the Polytechnic University for the efficient operation of the particulate traps it devised and which are now being sold through the newly listed Eco-Tek Holdings, one of only two approved distributors of such devices and the clear market leader.
The PolyU's tests clearly showed that emission reductions quickly fell below the trap's rated 30 per cent if the cleaning schedule was any less frequent and that this would also introduce the risk of spontaneous soot regeneration. In other words, we would get the soot right back in our lungs.
It is all very clearly laid out. Bring the vehicle in, un-clip the back portion of the trap (probably best not done with bare fingers if the engine has not cooled), pull out the wire mesh, put in a bucket of cleaning solution, swish it about, take it out again, clip it back inside the trap (perhaps cooler now) and Bob's your uncle.
Nuisance though it may be to busy taxi or PLB drivers, we shall just have to assume they are all doing it right on schedule. I am not about to do a tally with every Caltex station every night. Are you?
But at least it is a simple device and a cheap one, too. It costs us only HK$1,300 for each installation (yes, we the taxpayers pick up the bill, not the fleet operators) - goodness knows what the price would have been if we had instead adopted some of the particulate traps mentioned in a 1998 study done for the Environmental Protection Department.
It is all very well that tests on these more sophisticated devices cited figures in the 80 per cent and even the 90 per cent range for particulate reduction but they would undoubtedly have cost a good deal more than HK$1,300 apiece. Which is more important?