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Air Pressure In A Grow Room

indoor air air quality

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Poll: Indoor Air Quality (15 member(s) have cast votes)

What type of air pressure sets the stage for a number of indoor air quality problems?

  1. Positive (2 votes [13.33%])

    Percentage of vote: 13.33%

  2. Negative (3 votes [20.00%])

    Percentage of vote: 20.00%

  3. Neutral (0 votes [0.00%])

    Percentage of vote: 0.00%

  4. Static (10 votes [66.67%])

    Percentage of vote: 66.67%

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#1 Zoot

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Posted 01 November 2012 - 09:16 AM

I got that for a question on my test for indoor air quality based diagnostics. What do you think the answer is??? I know already, but lets see who else might know...
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#2 chow

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Posted 01 November 2012 - 10:46 AM

imo, you want negative air pressure in your grow room, but to your question, i would think static leads to problems? chow
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#3 mediuseA

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Posted 01 November 2012 - 11:55 AM

static is my call :D muA
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#4 HD96

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Posted 01 November 2012 - 12:35 PM

static Is my guess. shrugsmiley.gif
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#5 bongbonghi

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Posted 01 November 2012 - 12:39 PM

That was gonna be my guess but it is just a guess as I have no idea.
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#6 Zoot

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Posted 02 November 2012 - 06:10 AM

The answer is


NEGATIVE.....


Yep that's right, Negative air pressure is bad because it does not allow for a proper air exchange in the grow environment. Here's a cut & paste that explains why:





Speed of Growth

  • The speed at which plants grow is affected by atmospheric pressure conditions. At the 101 kPa pressure found in the Earth's atmosphere, each plant grows at its ideal rate. However, if you were to reduce this pressure, the plants would still grow, though not as quickly. If atmospheric pressure goes too low, a plant cannot survive due to the lack of gas exchange that can take place. Atmospheric pressure is important to the nutrition of growing plants.

Gas Concentration

  • More important than the actual atmospheric pressure number is the gas concentration. In the Earth's atmosphere, oxygen makes up about 20 percent of the gases present in the air. This is a required element for plant growth. Even if you reduce or increase the atmospheric pressure, it is important to maintain the same amount of oxygen for plant growth, which is about 15 to 20 kPa, regardless of the amount of atmospheric pressure.

Water Plants

  • The atmospheric pressure has a different effect on water plants than plants that grow in soil. The lower the atmospheric pressure, the less dissolved oxygen is present in the water. Therefore, at higher elevations, water plants do not grow as efficiently as they do at lower elevations. If there are fewer water plants present at higher elevations, they can still grow because fewer plants require less oxygen in the water. However, water at higher elevations is often colder, which allows for higher concentrations of oxygen. The two factors often balance each other out.

Adaptations

  • Unlike humans, plants are able to adapt to their environment and actually change their genetic makeup to survive in varying atmospheric pressure conditions, according to the National Academies Press. Plants can alter their metabolism to accommodate the varying gases present in different atmospheric pressure, surviving under pressures of less than 25 kPa. The plants may grow more slowly and may not achieve the same amount of growth, but they will still survive and produce seeds to create more plants.
Did you read the last line??? Produce seed, survive... Not good, I also read that if the pressure is to low it can cause plants to be leggy & stretch, like that of poor lighting. Not just that, but it can lock the plant up & interfere with the plants natural osmosis process.

As an after thought to all of this, maybe this explains why outdoor crops grow larger & give up greater yields? They are not victumes to indoor growers, who wish to suck the air out so fast that they throw off the proper air exchange rate???



That's enough out of me on this today, peace...... :Cookie: AND REMEMBER K.I.S.S.
LOL
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#7 mediuseA

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Posted 02 November 2012 - 08:05 AM

thinking.gif ....think ya missed sommat there, zoot...you are mixing up air pressure in the growroom/cab/tent with atmospheric pressure...air pressure in the growroom must be negative, so th@ inflowing air stops smell escaping until it is sucked through a filter....atmospheric pressure is in relation to the elevation above or below perceived sea level...I think outdoors crops get stronger light in a better spectrum, including uv light...and the natural airflow th@ would continually replentish co2...water temp plays a big role in how much oxygen the water can hold....warm water holds less oxygen....an airstone or h2o2 might be used to oxygenate warmer water....I would think below sealevel, where atmospheric pressure is greater would also leave plants further away from the light source [tonka as LC calls it :D eheheeeheee] which might account for stretching and lanky growth.

thinking.gif hmmmm ...could be wrong.....but th@'s how I see it

muA
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#8 Turf

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Posted 02 November 2012 - 08:48 AM

imo i dont think you have any control over atmospheric pressure. where ever you grow.... you will have the same column of air above creating the atmospheric pressure. putting a fan in the tent isn't gonna do much about changing that pressure.

Edited by Turf, 02 November 2012 - 08:50 AM.

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#9 Zoot

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Posted 02 November 2012 - 09:42 AM

Actually, by definition, atmospheric or air pressure is the force per unit of area exerted on the Earth’s surface by the weight of the air above the surface. The force exerted by an air mass is created by the molecules that make it up and their size, motion, and number present in the air. These are important factors because they determine the temperature and density of the air and thus its pressure. The greater the Negative pressure the denser the air & less gasses present.

The minimum pressure difference necessary to achieve and maintain negative pressure that will result in air flow into the room is very small only 0.001 inch of water gauge. The actual level of negative pressure achieved will depend on the difference in the ventilation exhaust and supply flows and the physical configuration of the room, including the air flow path and flow openings. To establish negative pressure in a room, the supply and exhaust air flows are balanced to achieve an exhaust flow of either 10% or 50 cfm greater than the supply (whichever is greatest). In most situations, this specification should achieve a negative pressure of at least 0.001 inch of water.

A 10% or 50 cfm difference is not that great to have between exhaust and intake but most growers use a passive air intake, which creates an imbalance in the air pressure thus causing the air to be less enriched.
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#10 mediuseA

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Posted 02 November 2012 - 10:18 AM

good info zoot....gonna hafta sit down and do the maths :lol: hehehe... I cannot see how a growroom might get enough negative pressure to influence the plant significantly growing plants in a mine in canada did really well, but I believe it was magnetic reasons th@ are credited with the growth no mention of the atmospheric/barometric influence muA
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#11 Zoot

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Posted 04 November 2012 - 07:38 AM

Here is some more info that I got from a molecular biologist Rob Ferl, director of Space Agriculture Biotechnology Research and Education at the University of Florida, & he states, "The problem is, in a low pressure environment, plants have to work hard to survive. Remember, plants have no evolutionary preadaption to hypobaria," says Ferl. There's no reason for them to have learned to interpret the biochemical signals induced by low pressure. And, in fact, they don't. They misinterpret them. Low pressure makes plants act as if they're drying out."

In recent experiments, supported by NASA's Office of Biological and Physical research, Ferl's group exposed young growing plants to low pressure for about twenty-four hours. In such a low pressure environment, water is pulled out through the leaves very quickly, and so extra water is needed to replenish it.

But, says Ferl, the plants were given all the water they needed. Even the relative humidity was kept at nearly 100 percent. Nevertheless, the plants' genes that sensed drought were still being activated. Apparently, says Ferl, the plants interpreted the accelerated water movement as drought stress, even though there was no drought at all. That's bad. Plants are wasting their resources if they expend them trying to deal with a problem that isn't even there. For example, they might close up their stomata -- the tiny holes in their leaves from which water escapes. Or they might drop their leaves altogether.


Now that is good info.


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#12 mediuseA

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Posted 04 November 2012 - 07:46 AM

Hmmmm... thinking.gif would low pressure for a few days immediately before harvest lead to faster drying buds perhaps? muA
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#13 Zoot

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Posted 04 November 2012 - 08:48 AM

If you were to cut off water & then drop the pressure in the room before harvest I would say yes. But that might also lead to buds not being as sticky. That might give reason as to why so many growers get different results, even though everything else is the same, the pressure differential is a variably that is wildly inconsistent and might be the root cause.
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#14 canon

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Posted 09 October 2013 - 10:13 PM

Gonna step in this pile some. Awhile back I was tought "Happy Plant" by a old guy on another site. Whole line is "Happy plants don't smell". I know, hard to believe and all. I rejected the notion for the longest time. Then I noticed from time to time they actually wouldn't smell for a few days. Really got interested into "why". Found out that indeed they were "happy". I'll just mention a few things and know not many will buy into it,, but if 1 person does try it, than the word has started. Keep the plant completely stress free. There's a relation ship of heat / humidity. Charts are available for the looking. Along with that, water just right, circulate air just right (very light air flow... NO WIND tunnels), and DON"T create a negative presure. Also, don't crowd them. I've come to the point of if I smell them, something is wrong. They are unhappy. I have a filter in the intake incorporated into the door. One day I noticed a little smell and thought "Hmmmm." Next day the stunk like hell. After a ton of trying things and pondering,, finally found the issue was a clogged filter. That created negative presure and stressed the plants and made them stink. Changed the filter and within 12 hrs. all smells gone again. If you could leave your room open for a day or two I'll bet most of the average rooms wouldn't have smelly (stressed) plants either. I know, hard to believe and all. but it IS true. I don't even own a filter anymore.

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