air exchange in terrarium - Orchid Board

travelfin · #1 12-21-2007, 01:41 PM

Anybody have facts on how much should the air change per hour. To my knowledge the air in a building changes once per two hours. Greenhouses run between once an hour to once per minute. If the air doesn't change how long does co2 last for the plants.
It is easy to have high humidity if the air changes slowly and very difficult if it changes fast.
Searched the net for an answer but found nearly nothing. Only for greenhouses.
Which is better slow change and high humidity 90%
or fast change and 70% humidity.

Ross · #2 12-21-2007, 02:15 PM

I don't have the info you are asking, however I would like to share my setup as it works great. I have two passive vents on one end of orchidarium and a thru-wall fan on opposite wall. I run this for 3 hours every night. During the lights-on period (right now 12 hours) there is no air exchange at all except if I open the doors to water. There is, however, a 12volt DC fan running 24/7 inside the tank blowing directly on the orchids. This arrangement has kept them happy and blooming for almost a year, now. Hope this helps.

travelfin · #3 12-21-2007, 02:25 PM

Thanks for the answer, if no scientific answers then answers based on experience help.
Running air in and out myself 24/7 and no fan inside

Ross · #4 12-21-2007, 02:28 PM

Quote:

Originally Posted by travelfin

Thanks for the answer, if no scientific answers then answers based on experience help.
Running air in and out myself 24/7 and no fan inside

Nothing wrong with that, at all. It's just that I want really high humidity for my Angraecoids, and running air thru the tank would defeat that (in my case.)

travelfin · #5 12-21-2007, 02:42 PM

Just trying to find out is air exchange co2 or high humidity more important and which one is the more important factor. And basically why in scientific terms.

Ross · #6 12-21-2007, 03:06 PM

I can tell you this - plants use CO2 during lights-on periods (day) to run processes necessary for growth, etc. They expell Oxygen during this same period. Related to chlorophyl production and maintenance. During lights-off periods, the process reverses and they consume Oxygen and expell CO2. The production of CO2 is at the heart of the war on "greenhouse gas production".

My personal observation is that (if growing humidity loving plants) the rating of the three things would be #1- humidity, #2-air exchange to reduce likelihood of molds and rot and I would not be concerned about CO2 at all. I doubt your tank is sealed so well as to be a mini-environment (a biosphere.) So normal opening of the doors for various tasks will cause a certain amount of air exchange on a basis directly related to the frequency you open the doors.

As to "scientific terms", I think it may relate to what you are growing. I grow mostly Angraecoids and they depend on high humidity and a steady source of "rain" because of the home territory. So in my case I can state, unequivocally, that humidity is the most important factor of the three you cite. Other important factors for me are control of temps, amount of light, a brief drying out to control rot and mold on the mounts, constant air movement, and brief (yet regular) mistings to simulate the ocean fog they might have experienced in nature.

This is a really interesting discussion. I wish some others would join in, because I am not an expert - I just have a bunch of success and observations.

travelfin · #7 12-21-2007, 03:47 PM

You are right, should I lower the air exchange for higher humidity for night time and have a higher humidity or mist more daytime for a higher humidity daytime.
Which is better more internal airflow inside the terrarium and less air change or the other way arround. Easy to do with timers. So what is the best and why

FinnBar · #8 12-21-2007, 03:55 PM

I don't think a universal answer exists. so much depends on the species, watering habits, and whatnot.
I prefer to mainly circulate the air but like Ross' my tank has mainly Aerangis. I've got a pretty vigorous fan on 24/7 which i moved to another angle as it was drying plants a little too well, even with 90+ humidity.

the tank is sealed quite well and most of the air exchange takes place while watering.
the conditions seems to suit the Aerangis but for example bulbophyllums i might try a little less air movement for starters..
the air moving up one side certainly creates microclimates within the limited space. maybe now i've learnt how to make use of it better.

i'd rather keep the humidity above 90 and circulate the air inside heavily than exchange the air more at the cost of humidity.

Ross · #9 12-21-2007, 04:08 PM

Quote:

Originally Posted by FinnBar

I don't think a universal answer exists. so much depends on the species, watering habits, and whatnot.
I prefer to mainly circulate the air but like Ross' my tank has mainly Aerangis. I've got a pretty vigorous fan on 24/7 which i moved to another angle as it was drying plants a little too well, even with 90+ humidity.

the tank is sealed quite well and most of the air exchange takes place while watering.
the conditions seems to suit the Aerangis but for example bulbophyllums i might try a little less air movement for starters..
the air moving up one side certainly creates microclimates within the limited space. maybe now i've learnt how to make use of it better.

i'd rather keep the humidity above 90 and circulate the air inside heavily than exchange the air more at the cost of humidity.

I learned a lot from one of your earlier posts (or was it an article) on the value of fans in the tank. Mine moves the plants around constantly.

travelfin · #10 12-23-2007, 10:05 AM

Just calculated that my small vivarium has about 11o gallons of air and the larger one has 230 gallons of air. Also reread a German book Orchideen kultur on orchids, where the author Gertrud Fast quoted a study where air exchange was changed from 30 x per hour to 60 x per hour and the results were really big. Better plants and better blooming. I have reasned so far Orchids are quite easy keep alive, to bloom them difficult and to grow show orchids extremely difficult. Have examples of plants growing very well Oertedella and the weight of the plant grows more arial roots and it drops deeper down and suddenly it starts slwing growth, less light and maybe moisture. Also have a Dendrobium tennelum first blooming 10 flowers, moved it to another spot roots damp water flows over them and was rewarded with 50 flowers.
Also thinking how much there is co2 in 100 gallons of air and for how long and how many plants will thrive on the co2. when I look at many rerrarium pictures there are maybe ten plants. I have in my 110 gallon 70 orchids and 30 other plants and moss. a big difference.

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