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{| {{table}}class="wikitable"

| Semi-permeable membrane (SPM) <ref name="semi"/>. ||Separate N2 and O<SUB>2</SUB> using a 'sieve' ||[[Intermittent Hypoxic Exposure]] and [[Intermittent Hypoxic Training at rest or while exercising]]||GO<SUB>2</SUB>Altitude||Minimal running costs, Stable 02 levels||Expensive to buy, Lower flow rates than PSAS

| Pressure swing absorption<ref name="psa"/> ||Different gases are absorbed at different rates under different pressures ||Live High, Train Low, Altitude tents or altitude rooms. <br>(Note Hypoxico systems also support [[Intermittent Hypoxic Exposure]] and [[Intermittent Hypoxic Training]].)||CAT, Hypoxico, and Higher Peak (same generator, different prices)||Minimal running costs, High flow rates at moderate O<SUB>2</SUB> concentrations||Expensive to buy, Poor performance at low O<SUB>2</SUB> concentrations

| Rebreather||Use of scrubber to absorb exhaled CO<SUB>2</SUB>, which then contains less O<SUB>2</SUB> and is rebreathed||[[Intermittent Hypoxic Training Exposure]] at rest ||AltO₂lab, AlitPower||Cheap to buy, Cheap to run (refilling cartridges)||Harder to control O<SUB>2</SUB> concentrations

I believe that the [[DIY Altitude Training]] (or similar [[AltoLab]] system ) is the most cost effective solution. For those wanting a sleep based system, Higher Peak offers the best value.  

Chemical generators use a chemical reaction to either remove oxygen from the air, or to remove the carbon dioxide from the air that you exhale, which is then breathed again. These systems are cheaper to purchase, but require the ongoing purchase of the chemical cartridges. These systems are only used for intermittent trainingExposure, not for sleeping.

[[AltoLab]] uses a stack of AltoMixers, with each AltoMixer diluting the oxygen to provide the equivalent of 5,000 ft. The [[AltoLab ]] system also requires a CO<SUB>2</SUB> scrubber which has to be replaced and lasts 2-3 hours. The running costs would be $10-15 per hour, but you can buy the CO<SUB>2</SUB> scrubber in bulk, reducing the cost down to $1 per hour; see [[AltoLab]] for details. http://www.altolab-usa.com/* The elite kit is $850 and contains 8 AltoMixers giving 5,000-40,000 ft of elevation, 12 silos (CO<SUB>2</SUB> scrubbers) proving 24 hours of usage, a pulse oximeter [[Pulse Oximeter]] and the masks. * The performance kit is $580 and contains 6 AltoMixers giving 5,000-30,000 ft of elevation, 6 silos (CO<SUB>2</SUB> scrubbers) proving 12 hours of usage, a pulse oximeter [[Pulse Oximeter]] and the masks.

AltiPower uses a system that removes the CO<SUB>2</SUB> from the exhaled air that is then rebreathed. It is not clear how long the cartridges last, or what altitude is achieved. The system appears equivalent to [[AltoLab]], but significantly more expensive. http://www.altipower.com * AltiPower Pro Kit, $1,000. Comes with 2 cartridges and [[Pulse Oximeter ]]

* MAG-10, $2,550300. Provides 20,000 ft. Base price for generator only* MAG-10 with tent, $32,050550 (Tent only covers head and shoulders)* MAG-10 with mask, $2,800400* The MAG-10 with mask, Oximeter (to measure blood oxygen saturation), $2,900===Hypoxico===Hypoxico systems is an established manufacturer. The prices shown below were what I was quoted in 2009. There are no published prices on http://www.hypoxico.com/ but some prices are shown at http://www.bikemania.biz/Altitude_Trainers_s/185.htm* Everest and Summit, $5,550. Provides 12,500 ft, or 21,000 ft with a $200 adapter. (Looks physically II generators look identical to Higher Peak MAG-10)* HYP123, $5,500. Provides 12,500 ft, or 21,000 ft with a $200 adapter. Upgrade to HYP100.* HYP100, $4,700. Provides 9,000 ft, or 14,500 ft with a $200 adapter. (21,000 ft for IHT with add on.) * Conversion for use in exercise - $700* Tents - $350+

Colorado [[Altitude Training ]] provide a wide variety of systems. The CAT 9 and CAT 12 air units provide air at the equivalent of 9,000 and 12, but do not publish prices000 feet respectively. The CAT systems have a 3 year warranty. * CAT-430 Walk-in Tent System with CAT-12 Air Unit $4,595 + $219 shipping* CAT-315 Walk-in Tent System with CAT-12 Air Unit $4,245 + $189 shipping* CAT 12 with Sleeping Mask Kit $3,620 + $99 shipping* CAT 12 with Exercise Mask Kit $3,495 + $99 shipping 

GO2Altitude focuses on systems for intermittent hypoxic training [[Intermittent Hypoxic Training]] rather than sleep systems and appear to use a semi-permeable membrane technique. The cheapest system is their One Person / Portable.Their focus seems to have changed to aviation usage and their web site is now http://www.hypoxic-training.com/* One Person / Portable 2010, $5,990 ($6,500 delivered). Provides 21,000 ft and comes with pulse oximeter[[Pulse Oximeter]], PC software and hoses/masks ==Oximeters==A pulse oximeters measures the level of oxygen saturation of the blood by shining a light through the skin, usually at the finger. Standalone pulse oximeters are available from Amazon for less than $100. Two popular oximeters are an unbranded model for $45 [http://www.amazon.com/Finger-Pulse-Oximeter-SM-110-Carry-Wrist/dp/B003TJH3LI Finger Pulse Oximeter SM-110] and the $100 [http://www.amazon.com/gp/product/B002CAPUWY Nonin GO<SUB>2</SUB>]. (I purchased the SM-110 and I'm very pleased with it.)

* [[The Science of Altitude Training]]

* [[Book Review – - Altitude Training and Athletic Performance]]* [[Intermittent Hypoxic TrainingExposure]] and [[The Science of Intermittent Hypoxic Training 101Exposure]]