Public Lab Research note


Alternate Design for H2S Cannister

by deepwinter | August 04, 2012 03:29 | 95 views | 3 comments | #3127 | 95 views | 3 comments | #3127 04 Aug 03:29

Read more: publiclab.org/n/3127


I wanted to make the H2S cannister more reusable, and avoid the use of tape (which is not reusable and creates a mess over time). I used the hole drilling design suggested in another research note, but pre-drilled before running an experiment and used wide rubber bands as the method of sealing the holes. I tested the seal as follow: I blew forcibly into the capsule to test the seal, and it took a lot of pressure to get air to escape. I didn't test it, but I conjectured that this was more pressure than would take to 'pop' the lid of most of the cannisters. The rubber bands I used are from bundling vegetables at the market. I did look for wider rubber bands, but couldn't find a source for any. These allow for about a 3/8 hole to be drilled. I used a piece of paper with equidistant holes to mark and then punch holes that could then be drilled out. This was the best process I could find for consistent fabrication of the holes. A second tier of holes could also be added for additional airflow. I also used rubber bands to attach cannisters to a stake. Another useful option could be to use the same rubber band(s) that seal the holes to attach cannisters to stakes in the field - this could be convient (rubber band is always with the cannister) or a drawback (rubber band breaks in the field, now nothing to close the cannister).

This is basically a riff on the cannister design ideas, which I hope adds some useful ideas to the discussion.


3 Comments

Cool Matthew! One of the things we were worried about was light leaks and how much that would disturb the paper which is light sensitive. We put holes in the bottom of the canister so that sunlight couldn't directly hit the holes- could you do the same rubberband process with the holes on the bottom?

A broader question for others... have we just tested the strips to see what they do when they are exposed to light and no H2S is present? I didn't see a note for this after a quick look.

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The rubber band won't work very well for sealing the bottom of the cannister, but a hood could be constructed to shield the holes, and held in place by the rubber band. I'll mock something up.

I also considered placing the strips in the cannister so that the emulsion side is up, and light wouldn't get on it. This could potentially mitigate light problems as well.

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Hi @deepwinter - We're going to do an OpenHour on exploratory hydrogen sulfide monitoring methods Monday, January 8th at 8pm ET/ 7 central. Hope you'll consider joining on!

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