From e8a7b58affde1dd75e8923802559e18f0e8e454b Mon Sep 17 00:00:00 2001
From: Atlantiscze <git@stepanekjakub.cz>
Date: Wed, 13 Aug 2014 11:24:12 +0200
Subject: [PATCH] N2 buildup fix attempt. Putting this into separate commit in
 case it's not wanted.

- Right now, air consists of 20% O2 80% N2 (approx.). Breathing takes O2 and turns it into CO2. CO2 gets scrubbed. Pressure drops, vents refill with air which again contains 80% N2 20% O2.
- This means that only 20% of breathed-out oxygen is replenished. Rest is replaced by N2. In large areas, such as Bar, with many mobs this can eventually lead to dangerous atmosphere status.
- This fix, while OOCly slightly unrealistic handles this issue by turning both O2 and N2 into CO2. Tested in CE's office with 5 human mobs without active scrubbers. Air lasts for 2~ hrs. Larger areas of course last significantly longer.
---
 code/modules/mob/living/carbon/human/life.dm | 34 ++++++++++++--------
 1 file changed, 21 insertions(+), 13 deletions(-)

diff --git a/code/modules/mob/living/carbon/human/life.dm b/code/modules/mob/living/carbon/human/life.dm
index 4af096131fc..020d87f27a8 100644
--- a/code/modules/mob/living/carbon/human/life.dm
+++ b/code/modules/mob/living/carbon/human/life.dm
@@ -459,7 +459,6 @@
 		var/safe_toxins_max = 0.005
 		var/SA_para_min = 1
 		var/SA_sleep_min = 5
-		var/inhaled_gas_used = 0
 
 		var/breath_pressure = (breath.total_moles()*R_IDEAL_GAS_EQUATION*breath.temperature)/BREATH_VOLUME
 
@@ -518,7 +517,6 @@
 				 // The hell? By definition ratio > 1, and HUMAN_MAX_OXYLOSS = 1... why do we even have this?
 				adjustOxyLoss(min(5*ratio, HUMAN_MAX_OXYLOSS))
 				failed_inhale = 1
-				inhaled_gas_used = inhaling*ratio/6
 
 			else
 
@@ -529,29 +527,39 @@
 
 		else
 			// We're in safe limits
-			inhaled_gas_used = inhaling/6
 			oxygen_alert = 0
-
+		var/exhale_amt = 0
 		switch(species.breath_type)
 			if("nitrogen")
-				breath.nitrogen -= inhaled_gas_used
+				exhale_amt = breath.nitrogen
+				breath.nitrogen = 0
 			if("phoron")
-				breath.phoron -= inhaled_gas_used
+				exhale_amt = breath.phoron
+				breath.phoron = 0
 			if("carbon_dioxide")
-				breath.carbon_dioxide-= inhaled_gas_used
+				exhale_amt = breath.carbon_dioxide
+				breath.carbon_dioxide = 0
 			else
-				breath.oxygen -= inhaled_gas_used
-
+				exhale_amt = (breath.oxygen + breath.nitrogen) // Haxy fix (see below)
+				breath.oxygen = 0
+				breath.nitrogen = 0
+		// Haxy fix - N2 buildup caused by breathing
+		// If you have room filled with breathing human mobs the oxygen level eventually reaches 0 even with vent.
+		// Our distro has 80% nitrogen and 20% oxygen (+-). However, humans take only part of this oxygen and convert it to CO2
+		// Basically, we change some oxygen into CO2, CO2 gets scrubbed, pressure drops a little, vents refill with N2 O2 mix.
+		// However, we didn't breath any nitrogen which eventually leads to O2 being mostly replaced with N2.
+		// This only happens with lots of mobs on one place, but may be actual for, for example, Dormitories.
+		// This fix causes mobs to turn all inhaled gas into CO2, which while hacky prevents this from happening.
 		if(!no_exhale)
 			switch(species.exhale_type)
 				if("oxygen")
-					breath.oxygen += inhaled_gas_used
+					breath.oxygen += exhale_amt
 				if("nitrogen")
-					breath.nitrogen += inhaled_gas_used
+					breath.nitrogen += exhale_amt
 				if("phoron")
-					breath.phoron += inhaled_gas_used
+					breath.phoron += exhale_amt
 				if("carbon_dioxide")
-					breath.carbon_dioxide += inhaled_gas_used
+					breath.carbon_dioxide += exhale_amt
 
 		// Too much exhaled gas in the air
 		if(exhaled_pp > safe_exhaled_max)