Well, they say to keep ventilation open (plugs out, etc.) and if extreme elevation, buy an oxygen generator. By extreme they generally mean more than 7000 feet, and say over 8000 feet hatching is next to impossible without oxygen unless hatching local eggs. They discuss details I can't remember without the book in front of me, which it isn't right now. I am not currently prepared to invest in an oxygen generator There is also discussion about reduced air pressure enhancing evaporation rates of incubating eggs.
Between the book and advice received on the NYD hatch thread I decided to try adding a humidifier to the room where the incubators and hatcher live, which is a small room with a door closed all the time, and it seems to have helped - the humidity in the Sportsman has stayed in the mid twenties which is fine. I don't add water to the incubator, only to the hatcher, where I raise humidity to mid 50s to mid 60s. Anyone who has hatched here knows it can be difficult to keep humidity where it needs to be for hatching. I fill the trays (1 and 2 in a 1588), plus a glass bowl with a white towel in it, with warmed water and a bit of Oxine (a couple of squirts of the solution we use to disinfect waterers and feed dishes).
My hatch rates have improved with these things, but overall improvement was most affected by getting the temp right in the incubator, which took buying a $20 Spot Check from Brinsea, and then two other $15 thermometers from ThermoWorks to verify. I checked all by placing the sensors in ice water, they were correct at 32 degrees and within a tenth of a degree of one another.
If I was just hatching a few eggs to expand my own flock I probably wouldn't nerd out on all these details, but I'm hatching chicks for sale from local flocks, and hatching eggs from breeds not currently available in this area to establish flocks for future availability of locally laid and hatched eggs, which increases overall suitability/tolerance for our climate and elevation.
This has been an extremely steep learning curve, and I've run the gamut of hatch rates - as low as zero on many shipped eggs, that didn't come free. As I explained to someone who sent me eggs from TN, 17 out of 50 hatching sounds really bad, but for shipped eggs at 5400+ feet of elevation, it's excellent. Expected hatch rate on shipped eggs to elevations of 5000 feet is 25% with all other conditions ideal (packaging, accuracy of temps, proper management of the eggs upon arrival, etc.).
You guys are KILLING me with all these hatchings! I'm going to have to call around this weekend and see if I can find some eggs. It's so much more fun hatching your own instead of buying chicks, at least for me anyway.