Filters are now volume-based.

code/modules/atmospherics/machinery/components/trinary_devices/filter.dm

@@ -4,7 +4,7 @@
 	desc = "Very useful for filtering gasses."
 	density = FALSE
 	can_unwrench = TRUE
-	var/target_pressure = ONE_ATMOSPHERE
+	var/transfer_rate = MAX_TRANSFER_RATE
 	var/filter_type = null
 	var/frequency = 0
 	var/datum/radio_frequency/radio_connection
@@ -15,7 +15,7 @@
 /obj/machinery/atmospherics/components/trinary/filter/examine(mob/user)
 	. = ..()
 	. += "<span class='notice'>You can hold <b>Ctrl</b> and click on it to toggle it on and off.</span>"
-	. += "<span class='notice'>You can hold <b>Alt</b> and click on it to maximize its pressure.</span>"
+	. += "<span class='notice'>You can hold <b>Alt</b> and click on it to maximize its flow rate.</span>"
 
 /obj/machinery/atmospherics/components/trinary/filter/CtrlClick(mob/user)
 	var/area/A = get_area(src)
@@ -31,8 +31,8 @@
 	var/area/A = get_area(src)
 	var/turf/T = get_turf(src)
 	if(user.canUseTopic(src, BE_CLOSE, FALSE,))
-		target_pressure = MAX_OUTPUT_PRESSURE
-		to_chat(user,"<span class='notice'>You maximize the pressure on the [src].</span>")
+		transfer_rate = MAX_TRANSFER_RATE
+		to_chat(user,"<span class='notice'>You maximize the flow rate on the [src].</span>")
 		investigate_log("Filter, [src.name], was maximized by [key_name(usr)] at [x], [y], [z], [A]", INVESTIGATE_ATMOS)
 		message_admins("Filter, [src.name], was maximized by [ADMIN_LOOKUPFLW(usr)] at [ADMIN_COORDJMP(T)], [A]")
 
@@ -150,24 +150,19 @@
 	var/datum/gas_mixture/air2 = airs[2]
 	var/datum/gas_mixture/air3 = airs[3]
 
-	var/output_starting_pressure = air3.return_pressure()
+	var/input_starting_pressure = air1.return_pressure()
 
-	if(output_starting_pressure >= target_pressure)
-		//No need to transfer if target is already full!
+	if((input_starting_pressure < 0.01))
 		return
 
 	//Calculate necessary moles to transfer using PV=nRT
 
-	var/pressure_delta = target_pressure - output_starting_pressure
-	var/transfer_moles
-
-	if(air1.temperature > 0)
-		transfer_moles = pressure_delta*air3.volume/(air1.temperature * R_IDEAL_GAS_EQUATION)
+	var/transfer_ratio = transfer_rate/air1.volume
 
 	//Actually transfer the gas
 
-	if(transfer_moles > 0)
-		var/datum/gas_mixture/removed = air1.remove(transfer_moles)
+	if(transfer_ratio > 0)
+		var/datum/gas_mixture/removed = air1.remove_ratio(transfer_ratio)
 
 		if(!removed)
 			return
@@ -188,10 +183,13 @@
 			removed.gases[filter_type] = 0
 			GAS_GARBAGE_COLLECT(removed.gases)
 
-			var/datum/gas_mixture/target = (air2.return_pressure() < target_pressure ? air2 : air1) //if there's no room for the filtered gas; just leave it in air1
+			var/datum/gas_mixture/target = (air2.return_pressure() < 9000 ? air2 : air1)
 			target.merge(filtered_out)
 
-		air3.merge(removed)
+		if(air3.return_pressure() <= 9000)
+			air3.merge(removed)
+		else
+			air1.merge(removed) // essentially just leaving it in
 
 	update_parents()
 
@@ -209,8 +207,8 @@
 /obj/machinery/atmospherics/components/trinary/filter/ui_data()
 	var/data = list()
 	data["on"] = on
-	data["pressure"] = round(target_pressure)
-	data["max_pressure"] = round(MAX_OUTPUT_PRESSURE)
+	data["rate"] = round(transfer_rate)
+	data["max_rate"] = round(MAX_TRANSFER_RATE)
 
 	data["filter_types"] = list()
 	data["filter_types"] += list(list("name" = "Nothing", "path" = "", "selected" = !filter_type))
@@ -227,21 +225,21 @@
 			on = !on
 			investigate_log("was turned [on ? "on" : "off"] by [key_name(usr)]", INVESTIGATE_ATMOS)
 			. = TRUE
-		if("pressure")
-			var/pressure = params["pressure"]
-			if(pressure == "max")
-				pressure = MAX_OUTPUT_PRESSURE
+		if("rate")
+			var/rate = params["rate"]
+			if(rate == "max")
+				rate = MAX_TRANSFER_RATE
 				. = TRUE
-			else if(pressure == "input")
-				pressure = input("New output pressure (0-[MAX_OUTPUT_PRESSURE] kPa):", name, target_pressure) as num|null
-				if(!isnull(pressure) && !..())
+			else if(rate == "input")
+				rate = input("New transfer rate (0-[MAX_TRANSFER_RATE] L/s):", name, transfer_rate) as num|null
+				if(!isnull(rate) && !..())
 					. = TRUE
-			else if(text2num(pressure) != null)
-				pressure = text2num(pressure)
+			else if(text2num(rate) != null)
+				rate = text2num(rate)
 				. = TRUE
 			if(.)
-				target_pressure = CLAMP(pressure, 0, MAX_OUTPUT_PRESSURE)
-				investigate_log("was set to [target_pressure] kPa by [key_name(usr)]", INVESTIGATE_ATMOS)
+				transfer_rate = CLAMP(rate, 0, MAX_TRANSFER_RATE)
+				investigate_log("was set to [transfer_rate] L/s by [key_name(usr)]", INVESTIGATE_ATMOS)
 		if("filter")
 			filter_type = null
 			var/filter_name = "nothing"

tgui/src/interfaces/atmos_filter.ract

@@ -3,10 +3,10 @@
     <ui-button icon='{{data.on ? "power-off" : "close"}}' style='{{data.on ? "selected" : null}}'
       action='power'>{{data.on ? "On" : "Off"}}</ui-button>
   </ui-section>
-  <ui-section label='Output Pressure'>
-    <ui-button icon='pencil' action='pressure' params='{"pressure": "input"}'>Set</ui-button>
-    <ui-button icon='plus' state='{{data.pressure == data.max_pressure ? "disabled" : null}}' action='pressure' params='{"pressure": "max"}'>Max</ui-button>
-    <span>{{Math.round(adata.pressure)}} kPa</span>
+  <ui-section label='Transfer Rate'>
+    <ui-button icon='pencil' action='rate' params='{"rate": "input"}'>Set</ui-button>
+    <ui-button icon='plus' state='{{data.rate == data.max_rate ? "disabled" : null}}' action='rate' params='{"rate": "max"}'>Max</ui-button>
+    <span>{{Math.round(adata.rate)}} L/s</span>
   </ui-section>
   <ui-section label='Filter'>
     {{#each data.filter_types}}