Great healthy growth continues and it’s time to introduce C02. My first-time trying CO2 supplementation. :>

Conditions: 1.2mS/cm. Ph 5.5 , CO2=800ppm, Light 18/6 @ 900PPFD, Day 80F-83F. Night 75F(min) RH Day 60% Night 50%

Presently without any CO2 supplement, the grow room starts the day about 450ppm and by the end of the day is down at 400ppm. From past grows, as plant mass increases the CO2 drops to 350 ppm range.

Let’s do the calculations to add CO2, raising the grow room to 800PPM CO2 and see if the numbers /cost is acceptable.

It’s important to understand.. Increasing CO2 levels in a grow room will quickly LOWER the Ph of recirculated irrigation water.. ( Forming more Carbonic acid). Especially if using an aeration pump, to keep the reservoir water oxygenated, have it outside the grow tent, drawing normal 400ppm air or the water reservoir will take a nose dive (lower) Ph.

Starting at 400ppm.. Want the grow room @ 800ppm.. Thus, we are raising the PPM by 400.

Calculations: 400PPM/1,000,000 gives us 0.0004… (Raise level 400ppm)

.0004 x (The volume of the grow room) = .0004 x (5’ x 9’ x 8’) = .144 cubic feet of CO2 needs to be added to raise the CO2 level from 400ppm to 800ppm.

Assume grow room air turnover rate of every 2 hours.. Thus need .144CF/2Hr = .072 CF/Hr

.072CF x 18 hours of lamps on = Need 1.296 CF of CO2 every 24 Hours (day)

20 Lb. CO2 bottle contains 20 lbs x 7.8CF/Lb. = 156 CF of CO2 in the bottle

Using 1.3CF/Day. 156CF/1.3CF/Day = 120 Day supply! ( Engineering says… This should work!)

Cost to fill 20Lb bottle of CO2 at local welding supply(welding grade gas) = $10 (cash).. Management say.. OK to proceed :>

The grow room is actually in a ‘Steady State” temperature and humidity during the day with the LED light on at 100%. With just some auxiliary heat at night. So, the exhaust fan operates minimally – an advantage to keep the CO2 in the grow tent.

Will be monitoring actual CO2 usage by weighing CO2 supply bottle. Started at 38lbs . (23lbs TARE + 15lbs CO2)