In the game, the crew feels equally well across the entire range of the CO2 scale: from 0 to 100% of the game scale. Based on the rate of CO2 accumulation in the game, a range of 0 - 100 game% CO2 is roughly equivalent to a volumetric CO2 content of 0 to 10%.
In real life, the body is able to tolerate 1 - 2% CO2 for some time (10 - 20% on the game scale), when 3% CO2 causes slight poisoning, nausea and vomiting. If the air contains 5% CO2 by volume, then impairments of consciousness occur, and working capacity is largely lost. 9 - 10% CO2 - loss of consciousness and death.
The air purification system of real U-boats kept CO2 up to 1.5% and O2 up to 17.5%.
According to the U-boat regulations, the CO2 content above 2% by volume (this is only 20% of the game scale!) was considered dangerous.
The measurement of CO2 and O2 concentration is carried out using Orsat instruments, for the first time after 4 hours of cruising under water, when the CO2 content should approach the maximum permissible value with the air purification system inactive. In addition, sampling tubes were available for the determination of CO2 content above 1.5%.
Based on the information provided in the VIIC U-boat technical documentation, we can draw the following conclusions:
A stock of 212 sodium hydroxide cartridges maintains 1.5% CO2 in the air for 72 hours. Only 12 sodium hydroxide cartridges can be in operation at a time (3 air cleaners with 4 cartridges each). The operating time of a set of 12 cartridges is: 12 * 72/212 = 4 hours.
Thus, the air purification system can be activated for periods of time that are multiples of 4 hours, with a total duration of no more than 72 hours during the patrol: this is at least 17 times for 4 hours.
TWoS now has the ability to activate the air purification system. However, this can only be done once per patrol. When the air purification system is activated, the rise in CO2 stops. CO2 freezes at the value where the air purification system is turned on. The air purification system is active for 12 hours. After 12 hours, the rise in CO2 resumes.
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