What I want to do
Compile under one note the parts, assembly, and calibration of my DIY formaldehyde test kit following @nshapiro's research on formaldehyde testing, my investigation of airflow (part 2) following ideas from from @davidmack, @gretchengehrke, @danbeavers, @nshapiro, and @warren and @nshapiro's work on photo cards, as well as some of my ideas on usability coming out of work on Lending Library Kits.
My attempt and results
- 3/4" drill bit
- 7/64" drill bit
- hand drill
- philips screwdriver
- DIY Formaldehyde Test Photo Card 1/page printout or 4/page printout
- Temperature Correction Lookup Chart(printout)
- $10.50 250ml polypropylene graduated cylinder
- $1.50 1/8" air barb (bought from local hardware store)
- $30 Tetra Whisper 100 air pump
- 1/8" valve (comes with air pump)
- $2.50 1 meter 1/8" PVC aquarium hose (bought from local hardware store)
- $0.50 #2 stopper with two 3/16" holes (part 2281-AA-1)
- $0.50 #3 stopper with 3/16" hole
- free 250ml glass bottle with wine-bottle sized (18mm) opening
- $0.50 3" of 1/2" brass tubing (hardware store)
- $1.50 corundum nail file (drug store)
- $4 Bubble solution (drug store), or DIY bubble solution (some combo of sugar, soap, & water)
- Free 1 quart plastic yogurt container lid as bubble solution tray
- 1/2" PTFE plumbing tape (from my stuff)
- $7 Kitagawa 710 Formaldehyde tube (1 box of 20 tubes costs $129 + shipping).
- $12 AvianWeb Thermometer/Hygrometer
Substitutions: a #3 stopper with two 3/16" holes would be better for a soda bottle or other plastic bottle as a stand.
We're going to convert the pump to suck rather than blow by turning the valve around. remove the four philips screws on bottom of the pump then do this:
GIF by @nshapiro
reassemble! one side should now be a vacuum pump.
valve attachment & tube holder
cut a small length of 1/8" tubing, attach to the small black screw valve that comes with the pump, and attach another roughly 50cm length of tubing to the other end of the pump. Push the 50cm tube into one of the #2 bottle stopper's holes:
Tubes can now be pushed into the other stopper hole. I am partial to stoppers because they hold the tubes better than the tubing alone, and keep me from putting my fingers near the broken tips. This glass bottle also provides a stable base lifting the tip of the tube up to 35cm above whatever surface its placed on. I think this is a little easier than @warren's "smellosaur" setup.
tube tip breaker
Drill a 7/64" hole in the brass tube to make a tip breaker.
tips can be pre-scored to break in the appropriate location either with a heart-shaped scorer that comes with the tubes. alternately, if you're like me and lost it, you can etch a circle around the tube with a corundum nail file:
graduated cylinder modification
drill a 3/8" hole in the bottom side of the graduated cylinder and screw the air barb in to cut threads into the plastic. Then screw it back out, wrap in teflon tape going right-wards so the tape doesn't bunch up when screwing the air barb back in.
There are two possible setups for calibration, attaching the graduated cylinder straight to the top of the formaldehyde tube, or using the bottle as a "dropout" to prevent bubbles from reaching the formaldehyde tube. This dropout setup is very likely better, and doesn't require one to watch the air line:
Notice in the dropout configuration the formaldehyde tube still needs its arrow pointed towards the pump, and has to be flipped upside down.
The calibration process is essentially: you wet down the walls of the graduated cylinder with bubble solution, and then dip the top in a tray of bubble solution to start a soap film, and then time its transit. We're shooting for 300ml/min (.3 Liters/m). Watch me calibrate:
In my case I didn't have the thermometer hygrometer I recommended, but i can use a thermometer in our space, and the humidity measurement from the weather report. Humidity is only an issue if it is below 5% or above 95%.
I set a 1/2 hour timer on my phone, filled out a test card, took a photo of the test card, ran the pump for 1/2 hour, and then corrected the reading for temperature using the temperature correction factor chart. Watch me run it:
Cards, before and after:
I immediately emailed myself the two photos, whose built-in EXIF time stamps and e-mail time stamp record constitute proof I ran a 1/2 hour test and wasn't overloading the tube.