DIY Incubator Ventilation

[Old McRonald]

I'm looking for people to chime in with incubator dimensions along with ventilation hole quantity and size, purchased or diy to get an idea of cubic inches of incubator to ventilation holes ratio for proper airflow.

Over the last couple of years I've had some pretty poor hatches even on very fertile eggs and one by one I have been eliminating variables. I have finally concluded it has to be poor ventilation, I only had 2 small holes in the lid believing that was enough. My last batch of duck eggs 10 of 12 were fertile and 6 made it to lockdown when I lost them as well. After giving them a couple of extra days all were completely formed and only needed to grow a little more and absorb the yolk, air space looked small also.

I have 2 hygrometers telling me 40-50% humidity increased to 60% for lockdown (also tried dry hatching with poor results as well) and 4 thermometers reading 99-100. Incubator was cleaned and sanitized with a 10% bleach solution. Eggs were turned 3 times daily so I feel pretty confident it was all due to ventilation. I have doubled the amount of ventilation holes as well as doubling the size of the original ones and the 2 new holes I added at the bottom of the incubator to get a better clean air exchange and I can still hold proper temp and humidity so I think I should be good now.

 

[NAA60512]

I am not an expert nor do I play one on TV, but I will chime in:

I was given to understand that an incubating egg requires .143 cubic feet of fresh air @ 20.95% oxygen content (sea level normal) per day by D18 of incubation. If you are incubating 10 eggs, you need 1.43 cubic feet of fresh air per day by D18, 20 eggs need 2.86 cubic feet of fresh air per day by D18, and so on.

Check my math on this, but I am pretty sure that .143 cubic feet per day is 0.0001 CFM (cubic feet per minute). According to the math, the 22 eggs I have in the incubator right now need 0.0022 CFM of fresh air by D18. If I max my DIY incubator out with 200 eggs I only need 0.02 CFM of fresh air. This is very close to the average "tidal volume" of a single adult human breath, about 0.018 cubic feet. That's not a huge gas exchange requirement and that is at my max capacity. I thought about installing a 30x30x7mm, 1.79 CFM Raspberry Pi cooling fan (it would fit perfectly over the exhaust port), but 1.79 CFM is 90x more air than I need for 200 eggs, and 814x more air than I need for 22 eggs.

I vent to control dehydration rather than supply oxygen. I am trying for a 13% moisture loss by weight by D18 of incubation, and I feel that as long as I am venting to control dehydration, sufficient oxygen exchange will happen as a result of that. I could care less about carbon dioxide. The average CO2 concentration in the air is about 400ppm (parts per million). CO2 levels under incubating hens have been measured at around 4000ppm. If a hen can make it work at 10 times normal CO2 concentration I am not going to worry about it in my small-scale incubator.

As far as calculating vent size, there is a formula for that but doing the math made my blood pressure spike. In my DIY 6.6 cubic foot beverage cooler incubator I just drilled a 28mm hole in the bottom and a 28mm hole in the top because I found some 28mm perforated black stainless steel covers on Amazon I wanted to use. I get plenty of exhaust air flow through the top vent, which draws fresh air in through the bottom intake vent.

Bottom (intake) vent

Top (exhaust) vent

Exhaust air flow (cover removed, sorry about the quality of the .gif, I rushed it)

 

[Old McRonald]

I am not an expert nor do I play one on TV, but I will chime in:

I was given to understand that an incubating egg requires .143 cubic feet of fresh air @ 20.95% oxygen content (sea level normal) per day by D18 of incubation. If you are incubating 10 eggs, you need 1.43 cubic feet of fresh air a day by D18, 20 eggs need 2.86 cubic feet of fresh air a day by D18, and so on.

Check my math on this, but I am pretty sure that .143 cubic feet per day is 0.006 cubic feet per hour, or 0.0001 cubic feet per minute. According to the math, the 22 eggs I have in the incubator right now need 0.132 cubic feet of fresh air per hour by D18, or 0.0022 cubic feet of fresh air per minute by D18.

For comparison, the average "tidal volume" of a single adult human breath is about half a litre or 0.018 cubic feet. There is ~8.2 times more air in a single adult human breath than my 22 eggs need in a minute.

I vent to control humidity rather than supply oxygen. I am trying for a 13% moisture loss by weight by D18 of incubation, and I feel that as long as I am venting to control dehydration, sufficient oxygen exchange will happen as a result of that. I could care less about carbon dioxide. The average CO2 concentration in the air is about 400ppm (parts per million). CO2 levels under incubating hens have been measured at around 4000ppm. If a hen can make it work at 10 times normal CO2 concentration I am not going to worry about it in my small-scale incubator.

As far as calculating vent size, there are formulae for that but doing the math made my blood pressure spike. In my DIY 6.6 cubic foot beverage cooler incubator I just drilled a 1.125" hole in the bottom and a 1.125" hole in the top. I covered the holes with perforated black stainless steel covers I found on Amazon just for looks. I get plenty of exhaust air flow through the top vent, which draws fresh air in through the bottom intake vent.

Bottom (intake) vent View attachment 1840814 Top (exhaust) vent
View attachment 1840800
Exhaust air flow (cover removed, sorry about the quality of the .gif, I rushed it)View attachment 1840799

Thanks for the numbers. I've made a spreadsheet so I can weigh eggs to the tenth of a gram and track my weight loss to equal 13% on day 18 for eggs weighing 50-65 grams on any given day, just need to number them and get initial weights and then random weights to track moisture loss to make adjustments. I will know what they should weigh on any given day if I wanted to go that far but will just check 1 or 2 a week should be sufficient. I enjoy the science and trying to dial it in now because I don't like losing unborn chicks.

 

[NAA60512]

I do exactly the same thing. I number the eggs, record their position on the egg turner, weigh them to a tenth of a gram on D01, D10, and D18, and my spreadsheet calculates individual and average loss. During the first 10 days of my current incubation my average loss was 2.5% greater than optimum, by D18 it was within 1% of optimum. I was a little dry early on.

 

[Old McRonald]

Good idea on the average weight loss. I will update mine also.