diff --git a/.development/tilda_tools.py b/.development/tilda_tools.py
index 44424f3..8557aac 100755
--- a/.development/tilda_tools.py
+++ b/.development/tilda_tools.py
@@ -124,8 +124,11 @@ def main():
         paths = args.paths if len(args.paths) else None
         if args.bootstrapped_apps:
             for k,val in list(resources.items()):
+                requested = paths and k in paths
+                bootstrapped = val.get("bootstrapped", False)
                 if val.get("type", None) == "app":
-                    if not k in paths and not val.get("bootstrapped", False):
+                    if not (bootstrapped or (paths and requested)):
+                        # App is not in the bootstrap list, and isn't explicitly requested
                         if args.verbose:
                             print("Removing app '{0}' from sync list".format(k))
                         del resources[k]
diff --git a/air_quality/main.py b/air_quality/main.py
new file mode 100644
index 0000000..1b863db
--- /dev/null
+++ b/air_quality/main.py
@@ -0,0 +1,198 @@
+"""This app needs an SDS011 sensor attacthed to UART 4 """
+
+___name___         = "Air Quality"
+___license___      = "MIT"
+___dependencies___ = ["sleep", "app", "ugfx_helper", "buttons", "homescreen"]
+___categories___   = ["EMF"]
+___bootstrapped___ = False # Whether or not apps get downloaded on first install. Defaults to "False", mostly likely you won't have to use this at all.
+
+import app 
+import ugfx, os, time, sleep
+from tilda import Buttons
+from tilda import Sensors
+from machine import Pin
+from machine import UART
+from machine import Neopix
+import random
+
+class DustSensorTester(object):
+
+    verbose = False
+
+    def contains_sequence (self,data, test):
+        """ Checks to see if the data sequence contains the test sewquence
+
+        Args:
+            data: sequence of data items
+            test: test sequence
+        Returns:
+            True if the test sequence is in the data sequence
+        """
+
+        if len(data)<len(test): return False
+
+        for pos in range(0,len(data)-len(test)+1):
+            if test == data[pos:pos+len(test)]: return True
+        return False
+
+class DustSensor(object):
+
+    verbose = False
+    fake_sensor = False
+
+    AWAITING_START = 0
+    READING_BLOCK = 1
+
+    def pump_byte(self, b):
+        """ Pump a byte into the block decode. Calls the decode method
+            when the block is complete
+
+        Args:
+            b: byte to pump
+        """
+        if self.state==self.AWAITING_START:
+            if self.verbose: print(self, "Awaiting start:", b)
+            if b==self.start_sequence[self.start_pos]:
+                # got a match - move to next byte in start sequence
+                self.start_pos = self.start_pos+1
+                if self.start_pos == len(self.start_sequence):
+                    # matched the start sequence
+                    self.block=self.start_sequence.copy()
+                    self.state=self.READING_BLOCK
+        elif self.state==self.READING_BLOCK:
+            if self.verbose: print("Reading block:", b)
+            self.block.append(b)
+            if len(self.block) == self.block_size:
+                self.state=self.AWAITING_START
+                self.start_pos=0
+                self.process_block()
+
+    def __init__(self, display):
+        self.display = display
+        self.state=self.AWAITING_START
+        self.start_pos = 0
+
+class sds011_sensor(DustSensor):
+    start_sequence = [0xaa,0xc0]
+    block_size = 10
+
+    def process_block(self):
+        """ Process a block of data obtained from the sensor
+            calls the new_reading method on the display to 
+            deliver a new reading or the error method
+            on the display to indicate an error
+        """
+        if self.verbose: print("sds011 process block")
+        if self.verbose: print([hex(x) for x in self.block])
+        check_sum = 0
+        for i in range(2,8):
+            check_sum = check_sum + self.block[i]
+        check_sum = check_sum & 0xff
+        if self.verbose: print("Checksum:",hex(check_sum))
+        if check_sum!=self.block[8]:
+            message = "Rcv:" + hex(self.block[8]) + " Cal:" + hex(check_sum)
+            self.display.error(message)
+            return
+        ppm10 = (self.block[4]+256*self.block[5])/10
+        ppm2_5 = (self.block[2]+256*self.block[3])/10
+        self.display.new_readings(ppm10,ppm2_5)
+    
+class Air_Quality_Display():
+    
+    def setup_screen(self):
+        """ Set up the screen and the labels that display
+            values on it. 
+        """
+        ugfx.init()
+        width=ugfx.width()
+        height=ugfx.height()
+        ugfx.clear(ugfx.html_color(0x800080))
+        style = ugfx.Style()
+        style.set_enabled([ugfx.WHITE, ugfx.html_color(0x800080), ugfx.html_color(0x800080), ugfx.html_color(0x800080)])
+        style.set_background(ugfx.html_color(0x800080))
+        ugfx.set_default_style(style)
+        ugfx.orientation(90)
+        ugfx.set_default_font(ugfx.FONT_TITLE)
+        ugfx.Label(0, 0, width, 60,"Air Quality", justification=ugfx.Label.CENTER)
+        label_height=45
+        self.ppm10_label = ugfx.Label(0, label_height, width, label_height,"PPM 10: starting", justification=ugfx.Label.CENTER)
+        self.ppm25_label = ugfx.Label(0, label_height*2, width, label_height,"PPM 2.5: starting", justification=ugfx.Label.CENTER)
+
+        self.temp_label = ugfx.Label(0, label_height*3, width, label_height,"Temp: starting", justification=ugfx.Label.CENTER)
+        self.humid_label = ugfx.Label(0, label_height*4, width, label_height,"Humid: starting", justification=ugfx.Label.CENTER)
+        self.error_label = ugfx.Label(0, label_height*5, width, label_height,"", justification=ugfx.Label.CENTER)
+        self.message_label = ugfx.Label(0, label_height*6, width, label_height,"", justification=ugfx.Label.CENTER)
+        self.error_count = 0
+        self.error_message = ""
+        self.neopix = Neopix()
+        self.p10_decode = ((100,0x00ff00),(250,0xffff00),(350,0xff8000),(430,0xff0000),(-1,0xcc6600))
+        self.p25_decode = ((60, 0x00ff00),(91, 0xffff00), (121,0xff8000),(251,0xff0000),(-1,0xcc6600))
+
+    def get_reading_color(self, value, decode):
+        for item in decode:
+            if item[0] < 0:
+                # reached the upper limit - return
+                return item[1]
+            if value < item[0]:
+                return item[1]
+    
+    def new_readings(self,ppm10_value, ppm25_value):
+        """ Called by the sensor to deliver new values to the screen.
+            Will also trigger the reading of the temperature and humidity
+            values.
+        """
+        self.ppm10_label.text("PPM 10: "+str(ppm10_value))
+        self.ppm25_label.text("PPM 2.5: "+str(ppm25_value))
+        temp = Sensors.get_hdc_temperature()
+        temp_string = "Temp: {0:2.1f}".format(temp)
+        self.temp_label.text(temp_string)
+        humid = Sensors.get_hdc_humidity()
+        humid_string = "Humidity: {0:2.1f}".format(humid)
+        self.humid_label.text(humid_string)
+        # Calculate some colours
+        self.neopix.display((self.get_reading_color(ppm25_value, self.p25_decode),self.get_reading_color(ppm10_value, self.p10_decode)))
+
+    def error(self, error_message):
+        """ Called by the sensor to deliver an error message. 
+        Args:
+            error_message: error message string
+        """
+        self.error_count = self.error_count + 1
+        self.error_label.text( "Errors: " +str(self.error_count))
+        self.message_label.text(str(error_message))
+
+display = Air_Quality_Display()
+display.setup_screen()
+
+sensor_port = UART(2,9600, bits=8, mode=UART.BINARY, parity=None, stop=1)
+
+sensor = sds011_sensor(display)
+
+def test_sensor():
+    """ Can be called to pump some test sequences into the sensor
+    """
+
+
+    test_sequences = [ ['0xaa', '0xc0', '0xf', '0x0', '0x22', '0x0', '0xe1', '0xdb', '0xed', '0xab'],
+        ['0xaa', '0xc0', '0x13', '0x0', '0x3e', '0x0', '0xe1', '0xdb', '0xb', '0xab'], # bad checksum
+        ['0xaa', '0xc0', '0x13', '0x0', '0x3e', '0x0', '0xe1', '0xdb', '0xa', '0xab'],
+        ['0xaa', '0xc0', '0x13', '0x0', '0x3e', '0x0', '0xe1', '0xdb', '0xd', '0xab'] ]
+
+    for test_sequence in test_sequences:
+        for ch in test_sequence:
+            sensor.pump_byte(int(ch))
+
+# test_sensor()
+
+buffer = bytearray([0])
+
+while (not Buttons.is_pressed(Buttons.BTN_A)) and (not Buttons.is_pressed(Buttons.BTN_B)) and (not Buttons.is_pressed(Buttons.BTN_Menu)):
+    while sensor_port.any() > 0:
+        sensor_port.readinto(buffer,1)
+        sensor.pump_byte(buffer[0])
+    sleep.wfi()
+
+ugfx.clear()
+
+app.restart_to_default()
+