diff --git a/adafruit_sgp30.py b/adafruit_sgp30.py
index 0b68b3f..d0ca369 100755
--- a/adafruit_sgp30.py
+++ b/adafruit_sgp30.py
@@ -29,6 +29,12 @@
 from adafruit_bus_device.i2c_device import I2CDevice
 from micropython import const
 
+try:
+    from typing import List, Tuple
+    from busio import I2C
+except ImportError:
+    pass
+
 __version__ = "0.0.0+auto.0"
 __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_SGP30.git"
 
@@ -80,7 +86,7 @@ class Adafruit_SGP30:
 
     """
 
-    def __init__(self, i2c, address=_SGP30_DEFAULT_I2C_ADDR):
+    def __init__(self, i2c: I2C, address: int = _SGP30_DEFAULT_I2C_ADDR) -> None:
         """Initialize the sensor, get the serial # and verify that we found a proper SGP30"""
         self._device = I2CDevice(i2c, address)
 
@@ -94,61 +100,63 @@ def __init__(self, i2c, address=_SGP30_DEFAULT_I2C_ADDR):
 
     @property
     # pylint: disable=invalid-name
-    def TVOC(self):
+    def TVOC(self) -> int:
         """Total Volatile Organic Compound in parts per billion."""
         return self.iaq_measure()[1]
 
     @property
     # pylint: disable=invalid-name
-    def baseline_TVOC(self):
+    def baseline_TVOC(self) -> int:
         """Total Volatile Organic Compound baseline value"""
         return self.get_iaq_baseline()[1]
 
     @property
     # pylint: disable=invalid-name
-    def eCO2(self):
+    def eCO2(self) -> int:
         """Carbon Dioxide Equivalent in parts per million"""
         return self.iaq_measure()[0]
 
     @property
     # pylint: disable=invalid-name
-    def baseline_eCO2(self):
+    def baseline_eCO2(self) -> int:
         """Carbon Dioxide Equivalent baseline value"""
         return self.get_iaq_baseline()[0]
 
     @property
     # pylint: disable=invalid-name
-    def Ethanol(self):
+    def Ethanol(self) -> int:
         """Ethanol Raw Signal in ticks"""
         return self.raw_measure()[1]
 
     @property
     # pylint: disable=invalid-name
-    def H2(self):
+    def H2(self) -> int:
         """H2 Raw Signal in ticks"""
         return self.raw_measure()[0]
 
-    def iaq_init(self):
+    def iaq_init(self) -> List[int]:
         """Initialize the IAQ algorithm"""
         # name, command, signals, delay
-        self._run_profile(["iaq_init", [0x20, 0x03], 0, 0.01])
+        self._run_profile(("iaq_init", [0x20, 0x03], 0, 0.01))
 
-    def iaq_measure(self):
+    def iaq_measure(self) -> List[int]:
         """Measure the eCO2 and TVOC"""
         # name, command, signals, delay
-        return self._run_profile(["iaq_measure", [0x20, 0x08], 2, 0.05])
+        return self._run_profile(("iaq_measure", [0x20, 0x08], 2, 0.05))
 
-    def raw_measure(self):
+    def raw_measure(self) -> List[int]:
         """Measure H2 and Ethanol (Raw Signals)"""
         # name, command, signals, delay
-        return self._run_profile(["raw_measure", [0x20, 0x50], 2, 0.025])
+        return self._run_profile(("raw_measure", [0x20, 0x50], 2, 0.025))
 
-    def get_iaq_baseline(self):
+    def get_iaq_baseline(self) -> List[int]:
         """Retreive the IAQ algorithm baseline for eCO2 and TVOC"""
         # name, command, signals, delay
-        return self._run_profile(["iaq_get_baseline", [0x20, 0x15], 2, 0.01])
+        return self._run_profile(("iaq_get_baseline", [0x20, 0x15], 2, 0.01))
 
-    def set_iaq_baseline(self, eCO2, TVOC):  # pylint: disable=invalid-name
+    def set_iaq_baseline(  # pylint: disable=invalid-name
+        self, eCO2: int, TVOC: int
+    ) -> None:
         """Set the previously recorded IAQ algorithm baseline for eCO2 and TVOC"""
         if eCO2 == 0 and TVOC == 0:
             raise RuntimeError("Invalid baseline")
@@ -157,9 +165,9 @@ def set_iaq_baseline(self, eCO2, TVOC):  # pylint: disable=invalid-name
             arr = [value >> 8, value & 0xFF]
             arr.append(self._generate_crc(arr))
             buffer += arr
-        self._run_profile(["iaq_set_baseline", [0x20, 0x1E] + buffer, 0, 0.01])
+        self._run_profile(("iaq_set_baseline", [0x20, 0x1E] + buffer, 0, 0.01))
 
-    def set_iaq_humidity(self, gramsPM3):  # pylint: disable=invalid-name
+    def set_iaq_humidity(self, gramsPM3: float) -> None:  # pylint: disable=invalid-name
         """Set the humidity in g/m3 for eCO2 and TVOC compensation algorithm"""
         tmp = int(gramsPM3 * 256)
         buffer = []
@@ -167,9 +175,9 @@ def set_iaq_humidity(self, gramsPM3):  # pylint: disable=invalid-name
             arr = [value >> 8, value & 0xFF]
             arr.append(self._generate_crc(arr))
             buffer += arr
-        self._run_profile(["iaq_set_humidity", [0x20, 0x61] + buffer, 0, 0.01])
+        self._run_profile(("iaq_set_humidity", [0x20, 0x61] + buffer, 0, 0.01))
 
-    def set_iaq_relative_humidity(self, celsius, relative_humidity):
+    def set_iaq_relative_humidity(self, celsius: float, relative_humidity: float):
         """
         Set the humidity in g/m3 for eCo2 and TVOC compensation algorithm.
         The absolute humidity is calculated from the temperature (Celsius)
@@ -185,7 +193,7 @@ def set_iaq_relative_humidity(self, celsius, relative_humidity):
 
     # Low level command functions
 
-    def _run_profile(self, profile):
+    def _run_profile(self, profile: Tuple[str, List[int], int, float]) -> List[int]:
         """Run an SGP 'profile' which is a named command set"""
         # pylint: disable=unused-variable
         name, command, signals, delay = profile
@@ -195,7 +203,9 @@ def _run_profile(self, profile):
         #   (name, ["0x%02x" % i for i in command], signals, delay))
         return self._i2c_read_words_from_cmd(command, delay, signals)
 
-    def _i2c_read_words_from_cmd(self, command, delay, reply_size):
+    def _i2c_read_words_from_cmd(
+        self, command: List[int], delay: float, reply_size: int
+    ) -> List[int]:
         """Run an SGP command query, get a reply and CRC results if necessary"""
         with self._device:
             self._device.write(bytes(command))
@@ -216,7 +226,7 @@ def _i2c_read_words_from_cmd(self, command, delay, reply_size):
             return result
 
     # pylint: disable=no-self-use
-    def _generate_crc(self, data):
+    def _generate_crc(self, data: bytearray) -> int:
         """8-bit CRC algorithm for checking data"""
         crc = _SGP30_CRC8_INIT
         # calculates 8-Bit checksum with given polynomial