diff --git a/README.md b/README.md
index 7404d14..f0b2c84 100644
--- a/README.md
+++ b/README.md
@@ -39,6 +39,9 @@ SOFTWARE.
  * `nether_book_`* (files starting with "nether_book"): Treer, 2019-2020
  * `nether_portal_ignition_failure.ogg`: Treer, 2019
  * `nether_particle_anim`* (files starting with "nether_particle_anim"): Treer, 2019
+ * `nether_fumarole.ogg`: Treer, 2020
+ * `nether_smoke_puff.png` is a derivative work of gleamyRock.gif by Spring (https://opengameart.org/users/spring), used 
+ under CC0 1.0. "Nether smoke puff" is licenced under CC BY-SA 4.0 Treer, 2020
 
 ### [Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0)](http://creativecommons.org/licenses/by-sa/3.0/)
  * `nether_rack.png`: Zeg9
diff --git a/mapgen_decorations.lua b/mapgen_decorations.lua
index cf7e443..2cfe8a1 100644
--- a/mapgen_decorations.lua
+++ b/mapgen_decorations.lua
@@ -25,12 +25,22 @@
 -- emerged or not before the decoration was placed.
 local allow_lava_decorations = nether.useBiomes
 
-local _ = {name = "air",                     prob = 0}
-local A = {name = "air",                     prob = 255, force_place = true}
-local G = {name = "nether:glowstone",        prob = 255, force_place = true}
-local N = {name = "nether:rack",             prob = 255}
-local S = {name = "nether:sand",             prob = 255, force_place = true}
-local L = {name = "default:lava_source",     prob = 255, force_place = true}
+local _  = {name = "air",                     prob = 0}
+local A  = {name = "air",                     prob = 255, force_place = true}
+local G  = {name = "nether:glowstone",        prob = 255, force_place = true}
+local N  = {name = "nether:rack",             prob = 255}
+local S  = {name = "nether:sand",             prob = 255, force_place = true}
+local L  = {name = "default:lava_source",     prob = 255, force_place = true}
+local F  = {name = "nether:fumarole",         prob = 255, force_place = true}
+local FS = {name = "nether:fumarole_slab",    prob = 255, force_place = true}
+local F1 = {name = "nether:fumarole_corner",  prob = 255, force_place = true, param2 = 0}
+local F2 = {name = "nether:fumarole_corner",  prob = 255, force_place = true, param2 = 1}
+local F3 = {name = "nether:fumarole_corner",  prob = 255, force_place = true, param2 = 2}
+local F4 = {name = "nether:fumarole_corner",  prob = 255, force_place = true, param2 = 3}
+local S1 = {name = "stairs:stair_netherrack", prob = 255, force_place = true, param2 = 5}
+local S2 = {name = "stairs:stair_netherrack", prob = 255, force_place = true, param2 = 7}
+local S3 = {name = "stairs:stair_netherrack", prob = 255, force_place = true, param2 = 12}
+local S4 = {name = "stairs:stair_netherrack", prob = 255, force_place = true, param2 = 16}
 
 
 -- =================
@@ -39,7 +49,7 @@ local L = {name = "default:lava_source",     prob = 255, force_place = true}
 
 local schematic_GlowstoneStalactite = {
     size = {x = 5, y = 10, z = 5},
-    data = {
+    data = { -- note that data is upside down
         _, _, _, _, _,
         _, _, _, _, _,
         _, _, _, _, _,
@@ -143,7 +153,7 @@ minetest.register_decoration({
 -- =======================================
 -- if player places a torch/block on this sand or digs it while standing on it, it sinks into lava
 
-if allow_lava_decorations then 
+if allow_lava_decorations then
     minetest.register_decoration({
         name = "Weak trap",
         deco_type = "schematic",
@@ -151,11 +161,11 @@ if allow_lava_decorations then
         sidelen = 80,
         fill_ratio = 0.002,
         biomes = {"nether_caverns"},
-        y_max = NETHER_CEILING, -- keep compatibility with mapgen_nobiomes.lua
-        y_min = NETHER_FLOOR,
+        y_max = nether.DEPTH, -- keep compatibility with mapgen_nobiomes.lua
+        y_min = nether.DEPTH_FLOOR,
         schematic = {
             size = {x = 4, y = 7, z = 4},
-            data = {
+            data = { -- note that data is upside down
                 _, _, _, _,
                 _, _, _, _,
                 _, N, _, _,
@@ -165,7 +175,7 @@ if allow_lava_decorations then
                 _, _, _, _,
 
                 _, N, _, _, -- make it look like a stalactite if it protrudes out the bottom of a landform
-                _, N, _, _, 
+                _, N, _, _,
                 N, L, N, _,
                 N, L, L, N,
                 N, L, L, N,
@@ -195,3 +205,195 @@ if allow_lava_decorations then
         rotation = "random"
     })
 end
+
+
+-- ==========================
+--    Fumaroles (Chimneys)
+-- ==========================
+
+
+local replacements_slab = {}
+local replacements_full = {["nether:fumarole_slab"] = "nether:fumarole"}
+
+if allow_lava_decorations then
+    -- Minetest engine limitations mean any mesh or nodebox node (like nether:fumarole)
+    -- will light up if it has lava below it, so replace the air node over the lava with
+    -- a node that prevents light propagation.
+    -- (Unfortunately this also means if a player digs down to get the lava block it'll
+    -- look like the lighting wasn't set in the block above the lava)
+    replacements_slab["air"] = "nether:airlike_darkness"
+    replacements_full["air"] = "nether:airlike_darkness"
+else
+    -- Lava is frequently removed by the old mapgen, so put sand at the bottom
+    -- of fumaroles.
+    replacements_slab["default:lava_source"] = "nether:sand"
+    replacements_full["default:lava_source"] = "nether:sand"
+end
+
+
+local schematic_fumarole = {
+    size = {x = 3, y = 5, z = 3},
+    data = { -- note that data is upside down
+        _, _, _,
+        _, N, _,
+        _, N, _,
+        _, _, _,
+        _, _, _,
+
+        _, N, _,
+        N, L, N,
+        N, A, N,
+        _, F, _,
+        _,FS, _,
+
+        _, _, _,
+        _, N, _,
+        _, N, _,
+        _, _, _,
+        _, _, _,
+    },
+}
+
+-- Common fumarole decoration that's flush with the floor and spawns everywhere
+
+minetest.register_decoration({
+    name = "Sunken nether fumarole",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 80,
+    fill_ratio = 0.005,
+    biomes = {"nether_caverns"},
+    y_max = nether.DEPTH,
+    y_min = nether.DEPTH_FLOOR,
+    schematic = schematic_fumarole,
+    replacements = replacements_full,
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y=-4
+})
+
+
+-- Rarer formations of raised fumaroles in clumps
+
+local fumarole_clump_noise_offset = -0.58
+local fumarole_clump_noise = {
+    offset = fumarole_clump_noise_offset,
+    scale = 0.5,
+    spread = {x = 40, y = 40, z = 15},
+    octaves = 4,
+    persist = 0.65,
+    lacunarity = 2.0,
+}
+
+fumarole_clump_noise.offset = fumarole_clump_noise_offset - 0.035
+minetest.register_decoration({
+    name = "Raised Nether fumarole",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 8,
+    noise_params = fumarole_clump_noise,
+    biomes = {"nether_caverns"},
+    y_max = nether.DEPTH,
+    y_min = nether.DEPTH_FLOOR,
+    schematic = schematic_fumarole,
+    replacements = replacements_full,
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y=-3
+})
+
+fumarole_clump_noise.offset = fumarole_clump_noise_offset
+minetest.register_decoration({
+    name = "Half-raised Nether fumarole",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 8,
+    noise_params = fumarole_clump_noise,
+    biomes = {"nether_caverns"},
+    y_max = nether.DEPTH,
+    y_min = nether.DEPTH_FLOOR,
+    schematic = schematic_fumarole,
+    replacements = replacements_slab,
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y=-3
+})
+
+fumarole_clump_noise.offset = fumarole_clump_noise_offset - 0.035
+minetest.register_decoration({
+    name = "Nether fumarole mound",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 8,
+    noise_params = fumarole_clump_noise,
+    biomes = {"nether_caverns"},
+    y_max = nether.DEPTH,
+    y_min = nether.DEPTH_FLOOR,
+    schematic = {
+        size = {x = 4, y = 4, z = 4},
+        data = { -- note that data is upside down
+            _, _,  _,  _,
+            _, N,  N,  _,
+            _, _,  _,  _,
+            _, _,  _,  _,
+
+            _, S,  S,  _,
+            N, A,  A,  N,
+            _, S2, S1, _,
+            _, F2, F1, _,
+
+            _, S,  S,  _,
+            N, A,  A,  N,
+            _, S3, S4, _,
+            _, F3, F4, _,
+
+            _, _,  _,  _,
+            _, N,  N,  _,
+            _, _,  _,  _,
+            _, _,  _,  _
+        },
+        yslice_prob = {{ypos = 3, prob = 192}} -- occasionally leave the fumarole cap off
+    },
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y = -2
+})
+
+fumarole_clump_noise.offset = fumarole_clump_noise_offset - 0.01
+minetest.register_decoration({
+    name = "Double Nether fumarole",
+    deco_type = "schematic",
+    place_on = {"nether:rack"},
+    sidelen = 8,
+    noise_params = fumarole_clump_noise,
+    biomes = {"nether_caverns"},
+    y_max = nether.DEPTH,
+    y_min = nether.DEPTH_FLOOR,
+    schematic = {
+        size = {x = 4, y = 5, z = 4},
+        data = { -- note that data is upside down
+            _, _,  _,  _,
+            _, N,  N,  _,
+            _, _,  _,  _,
+            _, _,  _,  _,
+            _, _,  _,  _,
+
+            _, S,  S,  _,
+            N, A,  A,  N,
+            _, S2, S1, _,
+            _, F2, F,  _,
+            _, _,  FS, _,
+
+            _, S,  S,  _,
+            F, A,  A,  N, -- the F may add slight variance in landforms where it gets exposed
+            _, S3, S4, _,
+            _, F3, F4, _,
+            _, _,  _,  _,
+
+            _, _,  _,  _,
+            _, N,  N,  _,
+            _, _,  _,  _,
+            _, _,  _,  _,
+            _, _,  _,  _
+        }
+    },
+    flags = "place_center_x,place_center_z,all_floors",
+    place_offset_y = -2,
+    rotation = "random"
+})
\ No newline at end of file
diff --git a/nodes.lua b/nodes.lua
index 14e3bd2..5e963a1 100644
--- a/nodes.lua
+++ b/nodes.lua
@@ -109,6 +109,15 @@ stairs.register_stair_and_slab(
 	default.node_sound_stone_defaults()
 )
 
+stairs.register_stair(
+	"netherrack",
+	"nether:rack",
+	{cracky = 2, level = 2},
+	{"nether_rack.png"},
+	S("Netherrack stair"),
+	default.node_sound_stone_defaults()
+)
+
 -- StairsPlus
 
 if minetest.get_modpath("moreblocks") then
@@ -122,6 +131,232 @@ if minetest.get_modpath("moreblocks") then
 end
 
 
+-- Fumaroles (Chimney's)
+
+local function fumarole_startTimer(pos, timeout_factor)
+
+	if timeout_factor == nil then timeout_factor = 1 end
+	local next_timeout = (math.random(50, 900) / 10) * timeout_factor
+
+	minetest.get_meta(pos):set_float("expected_timeout", next_timeout)
+	minetest.get_node_timer(pos):start(next_timeout)
+end
+
+-- Create an LBM to start fumarole node timers
+minetest.register_lbm({
+	label = "Start fumarole smoke",
+	name  = "nether:start_fumarole",
+	nodenames = {"nether:fumarole"},
+	run_at_every_load = true,
+	action = function(pos, node)
+		local node_above = minetest.get_node({x = pos.x, y = pos.y + 1, z = pos.z})
+		if node_above.name == "air" then --and node.param2 % 4 == 0 then
+			fumarole_startTimer(pos)
+		end
+	end
+})
+
+local function set_fire(pos, extinguish)
+	local posBelow  = {x = pos.x, y = pos.y - 1, z = pos.z}
+
+	if extinguish then
+		if minetest.get_node(pos).name      == "fire:permanent_flame" then minetest.set_node(pos,      {name="air"}) end
+		if minetest.get_node(posBelow).name == "fire:permanent_flame" then minetest.set_node(posBelow, {name="air"}) end
+
+	elseif minetest.get_node(posBelow).name == "air" then
+		minetest.set_node(posBelow, {name="fire:permanent_flame"})
+	elseif minetest.get_node(pos).name == "air" then
+		minetest.set_node(pos, {name="fire:permanent_flame"})
+	end
+end
+
+local function fumarole_onTimer(pos, elapsed)
+
+	local expected_timeout = minetest.get_meta(pos):get_float("expected_timeout")
+	if elapsed > expected_timeout + 10 then
+		-- The timer didn't fire when it was supposed to, so the chunk was probably inactive and has
+		-- just been approached again, meaning *every* fumarole's on_timer is about to go off.
+		-- Skip this event and restart the clock for a future random interval.
+		fumarole_startTimer(pos, 1)
+		return false
+	end
+
+	-- Fumaroles in the Nether can catch fire.
+	-- (if taken to the surface and used as cottage chimneys, they don't catch fire)
+	local inNether = pos.y <= nether.DEPTH and pos.y >= nether.DEPTH_FLOOR
+	local canCatchFire = inNether and minetest.registered_nodes["fire:permanent_flame"] ~= nil
+	local smoke_offset   = 0
+	local timeout_factor = 1
+	local smoke_time_adj = 1
+
+	local posAbove = {x = pos.x, y = pos.y + 1, z = pos.z}
+	local extinguish = minetest.get_node(posAbove).name ~= "air"
+
+	if extinguish or (canCatchFire and math.floor(elapsed) % 7 == 0) then
+
+		if not extinguish then
+			-- fumarole gasses are igniting
+			smoke_offset   = 1
+			timeout_factor = 0.22 -- reduce burning time
+		end
+
+		set_fire(posAbove, extinguish)
+		set_fire({x = pos.x + 1, y = pos.y + 1, z = pos.z},     extinguish)
+		set_fire({x = pos.x - 1, y = pos.y + 1, z = pos.z},     extinguish)
+		set_fire({x = pos.x,     y = pos.y + 1, z = pos.z + 1}, extinguish)
+		set_fire({x = pos.x,     y = pos.y + 1, z = pos.z - 1}, extinguish)
+
+	elseif inNether then
+
+		if math.floor(elapsed) % 3 == 1 then
+			-- throw up some embers / lava splash
+			local embers_particlespawn_def = {
+				amount = 6,
+				time = 0.1,
+				minpos = {x=pos.x - 0.1, y=pos.y + 0.0, z=pos.z - 0.1},
+				maxpos = {x=pos.x + 0.1, y=pos.y + 0.2, z=pos.z + 0.1},
+				minvel = {x = -.5, y = 4.5, z = -.5},
+				maxvel = {x =  .5, y = 7,   z =  .5},
+				minacc = {x = 0, y = -10, z = 0},
+				maxacc = {x = 0, y = -10, z = 0},
+				minexptime = 1.4,
+				maxexptime = 1.4,
+				minsize = .2,
+				maxsize = .8,
+				texture = "^[colorize:#A00:255",
+				glow = 8
+			}
+			minetest.add_particlespawner(embers_particlespawn_def)
+			embers_particlespawn_def.texture = "^[colorize:#A50:255"
+			embers_particlespawn_def.maxvel.y = 3
+			embers_particlespawn_def.glow = 12
+			minetest.add_particlespawner(embers_particlespawn_def)
+
+		else
+			-- gas noises
+			minetest.sound_play("nether_fumarole", {
+				pos = pos,
+				max_hear_distance = 60,
+				gain = 0.24,
+				pitch = math.random(35, 95) / 100
+			})
+		end
+
+	else
+		-- we're not in the Nether, so can afford to be a bit more smokey
+		timeout_factor = 0.4
+		smoke_time_adj = 1.3
+	end
+
+	-- let out some smoke
+	minetest.add_particlespawner({
+		amount = 12 * smoke_time_adj,
+		time = math.random(40, 60) / 10 * smoke_time_adj,
+		minpos = {x=pos.x - 0.2, y=pos.y + smoke_offset, z=pos.z - 0.2},
+		maxpos = {x=pos.x + 0.2, y=pos.y + smoke_offset, z=pos.z + 0.2},
+		minvel = {x=0, y=0.7, z=-0},
+		maxvel = {x=0, y=0.8, z=-0},
+		minacc = {x=0.0,y=0.0,z=-0},
+		maxacc = {x=0.0,y=0.1,z=-0},
+		minexptime = 5,
+		maxexptime = 5.5,
+		minsize = 1.5,
+		maxsize = 7,
+		texture = "nether_smoke_puff.png",
+	})
+
+	fumarole_startTimer(pos, timeout_factor)
+	return false
+end
+
+
+minetest.register_node("nether:fumarole", {
+	description="Fumarolic Chimney",
+	tiles = {"nether_rack.png"},
+	on_timer = fumarole_onTimer,
+	after_place_node = function(pos, placer, itemstack, pointed_thing)
+		fumarole_onTimer(pos, 1)
+		return false
+	end,
+	is_ground_content = true,
+	groups = {cracky = 3, level = 2, fumarole=1},
+	paramtype = "light",
+	drawtype = "nodebox",
+	node_box = {
+		type = "fixed",
+		fixed = {
+			{-0.5000, -0.5000, -0.5000, -0.2500, 0.5000, 0.5000},
+			{-0.5000, -0.5000, -0.5000, 0.5000, 0.5000, -0.2500},
+			{-0.5000, -0.5000, 0.2500, 0.5000, 0.5000, 0.5000},
+			{0.2500, -0.5000, -0.5000, 0.5000, 0.5000, 0.5000}
+		}
+	},
+	selection_box = {type = 'fixed', fixed = {-.5, -.5, -.5, .5, .5, .5}}
+})
+
+minetest.register_node("nether:fumarole_slab", {
+	description="Fumarolic Chimney Slab",
+	tiles = {"nether_rack.png"},
+	is_ground_content = true,
+	on_timer = fumarole_onTimer,
+	after_place_node = function(pos, placer, itemstack, pointed_thing)
+		fumarole_onTimer(pos, 1)
+		return false
+	end,
+	groups = {cracky = 3, level = 2, fumarole=1},
+	paramtype = "light",
+	drawtype = "nodebox",
+	node_box = {
+		type = "fixed",
+		fixed = {
+			{-0.5000, -0.5000, -0.5000, -0.2500, 0.000, 0.5000},
+			{-0.5000, -0.5000, -0.5000, 0.5000, 0.000, -0.2500},
+			{-0.5000, -0.5000, 0.2500, 0.5000, 0.000, 0.5000},
+			{0.2500, -0.5000, -0.5000, 0.5000, 0.000, 0.5000}
+		}
+	},
+	selection_box = {type = 'fixed', fixed = {-.5, -.5, -.5, .5, 0, .5}},
+	collision_box = {type = 'fixed', fixed = {-.5, -.5, -.5, .5, 0, .5}}
+})
+
+minetest.register_node("nether:fumarole_corner", {
+	description="Fumarolic Chimney Corner",
+	tiles = {"nether_rack.png"},
+	is_ground_content = true,
+	groups = {cracky = 3, level = 2, fumarole=1},
+	paramtype = "light",
+	paramtype2 = "facedir",
+	drawtype = "nodebox",
+	node_box = {
+		type = "fixed",
+		fixed = {
+			{-0.2500, -0.5000, 0.5000, 0.000, 0.5000, 0.000},
+			{-0.5000, -0.5000, 0.2500, 0.000, 0.5000, 0.000},
+			{-0.5000, -0.5000, 0.2500, 0.000, 0.000, -0.5000},
+			{0.000, -0.5000, -0.5000, 0.5000, 0.000, 0.5000}
+		}
+	},
+	selection_box = {
+		type = 'fixed',
+		fixed = {
+			{-.5, -.5, -.5, .5, 0, .5},
+			{0, 0, .5, -.5, .5, 0},
+		}
+	}
+
+})
+
+-- nether:airlike_darkness is an air node through which light does not propagate.
+-- Use of it should be avoided when possible as it has the appearance of a lighting bug.
+-- Fumarole decorations use it to stop the propagation of light from the lava below,
+-- since engine limitations mean any mesh or nodebox node will light up if it has lava
+-- below it.
+local airlike_darkness = {}
+for k,v in pairs(minetest.registered_nodes["air"]) do airlike_darkness[k] = v end
+airlike_darkness.paramtype = "none"
+minetest.register_node("nether:airlike_darkness", airlike_darkness)
+
+
 -- Crafting
 
 minetest.register_craft({
diff --git a/sounds/nether_fumarole.ogg b/sounds/nether_fumarole.ogg
new file mode 100644
index 0000000..e02c464
Binary files /dev/null and b/sounds/nether_fumarole.ogg differ
diff --git a/textures/nether_smoke_puff.png b/textures/nether_smoke_puff.png
new file mode 100644
index 0000000..10cb1db
Binary files /dev/null and b/textures/nether_smoke_puff.png differ