Smell of pencil shavings in tank air?

[fishblood]

We have a MAKO top of the line compressor at work. It is serviced on a regular basis. Filters changed etc. Our tank air has a very slight smell of PENCIL shavings. I know air usually has no smell, but I saw a thread on here that a pencil shaving smell can be normal. The thread did not get any further into the topic and it was from months ago.If anyone has some knowlege on this please let me know. I did call MAKO but they have not called me back. Thanks Jeff

 

[pescador775]

I have not heard of pencil shavings smell but I'll rush downstairs and open the sharpener; sorry, cooking a ham and that is all I can smell. Old socks, smokey, Diesel odor, funky chemical smell, these are, or used to be, common complaints. I emphasize that these are complaints from the past. Since charcoal is the last line of defense against odor, the problem may be that the charcoal is soaked. Pencil shavings contain graphite which is another name for charcoal. Make sure particles are not blowing through the hose. There is a phenomenon called desorption in which high temps cause charcoal to release some volatiles previously captured. Any of these issues would be very unusual in a well maintained compressor so it does not seem likely. The fill hose itself is another possible source of odor. Sometimes, a new compressor will produce an odor that is not blocked by charcoal. That ceases after about 50 tank fills. Finally, there are different kinds of activated charcoal.
Aluminum cylinders may develop a funky odor if water is present inside. The link below is an adsorption chart for various chemicals passing through a charcoal bed.



Activated Carbon Capacity Index Chart Explanation

 

[iain/hsm]

But what if it smells of a colored pencil what is the colour? Now I guess I have to miss spell it as color to keep you lot happy. LOL

IMHO my take is that the adsorbsion of odour is achieved from the activated charcoal or activated carbon in the filter tower and is called adsorbsion not absorbsion and I agree with what Pescador 775 says.

Reason is when the chemical gets wet anything adsorbed by the chemical (when wet) will simply flow off back off the chemical into the divers cylinder or tank. unlike if it was absorbed like water vapour in molecular sieve it will not.

The chemical itself, the activated carbon/charcoal can be made from a number of raw products: For fish tanks for filtering the crap out of the tank it is made from wood, for diving applications it should be made from coconut husks. Coal is another raw material

IMHO problem comes when the chemical supplier thinks fish tank...water...diving thats OK and the filter manufacturer/supplier is to mean to pay the higher cost of coconuts and in looking to save money uses an activated carbon/charcoal made from wood. (hence the wood shaving smell) or its imported from China in which case its all crap chemical to begin with.

This IMHO is where the mix up starts and when we as divers get to chat about the colour of the pencil and the smell in the tank. On the other hand it could be me talking crap, and as a final comment to that effect. How does a mathematician cure constipation? He can work it out with the pencil LOL

 

[pescador775]

Heh, Bob Hope you are not but still pretty funny. Yeah, the only thing I could think of was that the charcoal was wood or Chinese buffalo chips, heated in a retort and treated with phosphoric acid. I think the coconut shell base that has been cooked and steamed should give better results.