diff --git a/air purifier.scad b/air purifier.scad
new file mode 100644
index 0000000..0217296
--- /dev/null
+++ b/air purifier.scad	
@@ -0,0 +1,103 @@
+
+filter_x = 368; // mm
+filter_y = 494; // mm
+filter_z = 44; // mm
+
+module filter() {
+  // https://airfiltration.ca/collections/pleated-merv-plus/products/merv-13-2inch?variant=19413155348547
+  // merv-13 15x20x2
+  cube([filter_x, filter_y, filter_z]); 
+};
+
+fan_box_x = 255; // mm
+fan_box_y = 130; // mm
+fan_box_z = 43; // mm
+module fan_box() {
+  cube([fan_box_x, fan_box_y, fan_box_z]);
+};
+
+fan_mounting_hole_radius = 3; // mm
+fan_mounting_hole_length = 56; // mm
+
+module fan_plate_mounting_hole() {
+    // 56 mm length, which is 50mm between circle centers
+    hull() {
+        circle(fan_mounting_hole_radius, $fn=360);
+        translate([fan_mounting_hole_length - 2*fan_mounting_hole_radius, 0, 0]) {
+            circle(fan_mounting_hole_radius, $fn=360);
+        }
+    };
+}
+
+fan_plate_x = 353; // mm
+fan_plate_y = 229; // mm 
+fan_plate_z = 1; // mm
+module fan_plate() {
+    linear_extrude(fan_plate_z) {
+        difference() {
+            offset(r=1, $fn=360) {
+                // 353x229 but reduced for offset
+            square([fan_plate_x-1, fan_plate_y-1]);
+            }
+            
+     // @TOOD: Fix the translation values
+     translate([10, 10, 0]) {  rotate([0, 0, 45]) {                 fan_plate_mounting_hole();
+     }; };
+     translate([10, 218, 0]) {  rotate([0, 0, -45]) {                 fan_plate_mounting_hole();
+     }; };
+     
+     
+     translate([310, 180, 0]) {  rotate([0, 0, 45]) {                 fan_plate_mounting_hole();
+     }; };
+     translate([300, 50, 0]) {  rotate([0, 0, -45]) {                 fan_plate_mounting_hole();
+     }; };
+     };
+     
+    };
+};
+
+fan_cable_spacing = 30; //mm
+fan_box_offset_x = 48; // mm
+fan_box_offset_y = 50; // mm
+fan_box_offset_z = 1; // mm
+module fan() {
+   // https://acinfinity.com/hvac-home-ventilation/exhaust-fans/crawlspace-basement-fans/airtitan-s7-crawlspace-fan-with-speed-controller-12-inch/
+   // AirTitan S7 crawlspace fan
+   union() {
+     translate([fan_box_offset_x, fan_box_offset_y, fan_box_offset_z]) {
+       fan_box();
+     };
+     fan_plate();
+   }; 
+};
+
+
+side_wall_x =  5; // mm
+side_wall_y =  fan_box_y + 2*filter_z + 2*fan_cable_spacing;
+echo("Side wall:", side_wall_y, "by", side_wall_z);
+side_wall_z = filter_y; // mm
+module side_wall() {
+    // from rona
+    cube([side_wall_x, side_wall_y, side_wall_z], center=false);
+}
+
+#fan();
+
+// leave 30mm for the power cable gland
+// that comes off the fan_box
+translate([-(filter_x - fan_plate_x)/2, filter_z - fan_cable_spacing , fan_plate_z]) {
+rotate([90, 0, 0]) {
+#filter();
+}};
+
+// leave 30mm for the power glang
+// that comes off the fan_box
+translate([-(filter_x - fan_plate_x)/2, fan_plate_y + fan_cable_spacing, fan_plate_z]) {
+rotate([90, 0, 0]) {
+#filter();
+}};
+
+translate([-2, -20, fan_plate_z]) {
+#side_wall();};
+translate([filter_x, -20, fan_plate_z]) {
+#side_wall();};
\ No newline at end of file
diff --git a/crbox-corner-44x5-v1-pair.3mf b/crbox-corner-44x5-v1-pair.3mf
new file mode 100644
index 0000000..39ca499
Binary files /dev/null and b/crbox-corner-44x5-v1-pair.3mf differ