near-infrared diode sensor for carbon dioxide, carbon monoxide and methane

September 7, 2007

A pollution indicator on our car dashboard?
Posted by Roland Piquepaille

This might soon be possible according to researchers at the University of Manchester. They’ve designed a near-infrared diode laser sensor able to record levels of carbon dioxide, carbon monoxide and methane directly from your car’s exhaust..

This system has been developed by Dr Philip Martin of the School of Chemical Engineering and Analytical Science (CEAS) at The University of Manchester…”


Carbon Monoxide: convert gpm to ppm

September 7, 2007

In the US, car pollution is regulated by specifying gpm (grams per mile) limits. But the usual CO measurement is in ppm (parts per million). How to convert between these units?

Air weighs about 1.2 g per Liter. Warmer air would be less dense, and weigh less.

An old 1989 Volvo in Massachusetts is allowed up to about 30 gpm by state regulation, tested every two years. It is currently testing at about 10 gpm (8.4 gpm), although in previous years it has ranged from 3 to 25 gpm. (Just missed the general implementation by 1990 of a vehicle emissions limit of 3.4 gpm (grams per mile), a large reduction from the previous limit of 87 gpm.)

At idle, it takes about 3 seconds to fill an ordinary plastic shopping bag from the tailpipe. The bag measures about 11.5 L (Liter), so this is about 4 L per sec. If we guess that this idle engine load is equal to travelling at about 4 mph, this works out conveniently to about 1 L per sec per mph, which is also equal to about 1 g of air.

At 1 mph, it would take 3600 seconds to go one mile, putting out 3600 L with a mass of 3600 g. 10 g of CO for one mile, divided by 3600, works out to about 2800 ppm of CO.

2800 ppm would be at a similar level to smoking a cigarette, in terms of CO concentration. Breathing in the vicinity of such exhaust, if you were exposed to air diluted by 28 times, that would be 100 ppm. Not healthy, but not too terrible for a brief exposure for an ordinary healthy person.

Now let’s check against deriving ppm straight from the gpm. A mile is 1609 meters. Consider a car driving one mile, at any speed. Leaving behind an exhaust column of air, 1609 m by 10 cm by 10 cm. 16 m^3. One m^3 equals 1000 Liters, weighing 1000 g. 10 g of CO divided by 16,000 g of air would be 625 ppm, not too out of wack with the previous calculation.

If you are standing next to a stream of moving traffic, if the exhaust of each vehicle were mixed with a cross-section of at least 1 m by 1 m of air, which kept getting replaced with fresh air by convection/diffusion/wind, that would be a dilution of at least a factor of 100, reducing exposure to no more than 6 ppm of CO. Not much of a health concern, though not a good thing for repeated or continuous chronic exposure, particularly for the most vulnerable.

How do these theoretical calculations compare to reality? The higher levels should be easy to measure with current cheap digital home CO detectors, although they may not be very accurate. The lower levels will be harder to check. Current US home monitors are required to not show levels below 30 ppm, to reduce nuisance alarms. They can be forced to show lower levels, as a stored peak reading, but even that function is typically limited to readings over 10 ppm.

Presumably, badly adjusted cars may pollute substantially more. And all vehicles probably pollute more when first started, as they warm up. Most catalytic converters have to warm up before they work well at converting the CO. It is said that internal combustion vehicles can put out up to 25% CO (250,000 ppm).


Do you see a calculation mistake?
Is there a better way to think this through?

Hello there, world!

September 6, 2007

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Recycle alkaline batteries and CFLs at IKEA

July 5, 2007

IKEA invites customers to recycle compact fluorescent light bulbs (CFLs) and alkaline batteries at their stores. There are not many places to recycle CFLs, and hardly any places to recycle alkaline batteries, so this is unusual and very welcome.

At the IKEA in Stoughton Massachusetts (IKEA Stoughton MA), these items can be readily recycled in the customer service area, by the exit. It is unclear whether this offer is intended to include non-IKEA items, but the drop-off receptacle is unsupervised, and customers are leaving all brands of batteries. It is hard to guess how many items one would be able to drop off at once, without attracting undue attention. And there seems to be little assurance that CFLs deposited will not break, which seems like a poor design.

IKEA declares an emphasis on social and environmental responsibility. It is impressive that their big-box store is up on stilts, with the parking underneath. And that they have a “green roof”, with plants on top. (So they say… where is the proof? There are no photos.)

While it is good that they offer to recycle the alkaline batteries that they sell (mostly AA?), it is peculiar that the reason they offer is the mercury content (which should be minimal these days). If they were truly concerned about the environmental impact of such batteries, they would aggressively promote rechargeable Ni-MH batteries as alternatives to alkalines.

They do aggressively promote CFLs as alternatives to standard incandescent bulbs. Their standard E26-base bulb is impressively compact, the size and shape of an ordinary bulb, rated at 530 Lumens for 11 Watts (a respectable 48 L/W efficiency) 10,000 hours. 2 for $10 (but sometimes cheaper at other locations). They also offer a spherical over-sized 20W E26-base bulb, and assorted compact-tube bulbs, some modular.

Those offerings are unremarkable; Home Depot probably does better. But their low-wattage, small-size, small-base CFLs are very unusual. They offer small, rounded 7W 10,000 hr E12 candelabra-base bulbs, and even smaller blunt-pointed 5W 10,000 hr E12 bulbs. And a unique 7W 8,000 hr E17 reflector bulb. These are intended for use with their line of economy-priced desk, table and wall light fixtures.

The store also carried an unusual red CFL — amazingly inefficient, 5 lumens for 7 watts? A great opportunity for an LED light bulb?

Their brochures and reports proclaim their “corporate social responsibility”, but it is difficult to obtain further detailed information.

To be learned: what does their roof really look like, how much green is there? Is the public allowed up to see? What does the Stoughton facility do with runoff water? What actually happens with the CFLs left for recycling? What actually happens with the batteries left for recycling?

IKEA light bulbs
(get them to list lumens, watts, lumens per watt)

American dog tick from Pennsylvania

June 21, 2007

On Monday 18jun07 found a large black tick, over 1/8-in long, attached to upper arm. Apparently brought home from rural NE Pennsylvania, US.

There seem to be no good web sites for general identification of ticks. The Wikipedia article is not very good.

These are Pennsylvania-oriented sites:

Pulling with tweezers did not remove it. Water had no effect. A sharp hot soldering iron in close proximity disturbed it but killed it without convincing it to withdraw. Applying heat or any other irritant is inadvisable, because it may stimulate the tick to regurgitate into the host, increasing the chance of infection. It was removed intact by cutting the attached skin, with diagonal pliers cleaned with alcohol. The officially sanctioned procedure is to grasp firmly by the head/mouth with sharp tweezers and pull slowly and firmly until it comes out. Dig out any remaining parts from the skin, and disinfect site with alcohol etc. Save the tick in case of illness so that a more accurate diagnosis can be made, in the freezer and/or alcohol.

Identification by eye was difficult, without a good gallery of images to compare to. It seemed to be an American dog tick or a Lone Star tick (adult female), partly due to the large size. Unlikely to be a carrier of Lyme disease. Small possibility of carrier of Rocky Mountain Spotted Fever.

Scanning images into the computer the next day gives a much better look. Definitely seems to be an American dog tick, Dermacentor variabilis — about the most common tick in the US. The Wikipedia article is just a stub. Here are some good sites:
*[Article on American dog tick.] Harvard University – Ticks of New England: Fact Sheet and Gallery
*[Ohio State University Extension Fact Sheet]
*[Illinois] photographs, big and beautiful
*[Iowa tick images]

American dog tick, adult female. NE Pennsylvania, US.

Note intact mouth parts, embedded in skin of host.

American dog tick, bottom view, adult female. NE Pennsylvania, US.

greentech blog

June 13, 2007

This blog is dedicated to the environmental aspects of technology and the technical aspects of environmentalism — particularly in New England and the US. The focus will be on detailed technical exploration and discussion.