diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..b539f90
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,5 @@
+aiohttp==.3.9.5
+pyproj==3.6.1
+pytest
+async-timeout==4.0.3
+pytest-asyncio==0.23.7
\ No newline at end of file
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 0000000..8bd0e5f
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,5 @@
+[tool:pytest]
+testpaths = tests
+norecursedirs = .git
+addopts = -s -v
+asyncio_mode = auto
\ No newline at end of file
diff --git a/src/open_irceline/__init__.py b/src/open_irceline/__init__.py
new file mode 100644
index 0000000..a791cf4
--- /dev/null
+++ b/src/open_irceline/__init__.py
@@ -0,0 +1,4 @@
+from pyproj import Transformer
+
+project_transform = Transformer.from_crs('EPSG:4326', 'EPSG:31370', always_xy=True)
+rio_wfs_base_url = 'https://geo.irceline.be/rio/wfs'
diff --git a/src/open_irceline/api.py b/src/open_irceline/api.py
new file mode 100644
index 0000000..678259a
--- /dev/null
+++ b/src/open_irceline/api.py
@@ -0,0 +1,107 @@
+import asyncio
+import socket
+from datetime import datetime, timedelta
+from typing import Tuple, List
+
+import aiohttp
+from aiohttp import ClientResponse
+import async_timeout
+
+from . import project_transform, rio_wfs_base_url
+from .data import RioFeature, FeatureValue
+
+
+class IrcelineApiError(Exception):
+    """Exception to indicate a general API error."""
+
+
+class IrcelineApiCommunicationError(IrcelineApiError):
+    """Exception to indicate a communication error."""
+
+
+class IrcelineApiParametersError(IrcelineApiError):
+    """Exception to indicate a parameter error."""
+
+
+class IrcelineClient:
+    """API client for IRCEL - CELINE open data"""
+
+    def __init__(self, session: aiohttp.ClientSession) -> None:
+        self._session = session
+
+    @staticmethod
+    def epsg_transform(position: Tuple[float, float]) -> tuple:
+        """
+        Convert 'EPSG:4326' coordinates to 'EPSG:31370' coordinates
+        :param position: (x, y) coordinates
+        :return: tuple of int in the EPSG:31370 system
+        """
+        result = project_transform.transform(position[0], position[1])
+        return round(result[0]), round(result[1])
+
+    async def get_rio_value(self,
+                            timestamp: datetime,
+                            features: List[RioFeature],
+                            position: Tuple[float, float]
+                            ) -> dict:
+        coord = self.epsg_transform(position)
+        # Remove one hour from timestamp to handle case where the hour just passed but the data is not yet there
+        # (e.g. 5.01 PM, but the most recent data is for 4.00 PM)
+        timestamp = timestamp.replace(microsecond=0, second=0, minute=0) - timedelta(hours=1)
+
+        querystring = {"service": "WFS",
+                       "version": "1.3.0",
+                       "request": "GetFeature",
+                       "outputFormat": "application/json",
+                       "typeName": ",".join(features),
+                       "cql_filter": f"timestamp>='{timestamp.isoformat()}' AND "
+                                     f"INTERSECTS(the_geom, POINT ({coord[0]} {coord[1]}))"}
+
+        r: ClientResponse = await self._api_wrapper(rio_wfs_base_url, querystring)
+        return self.format_result('rio', await r.json())
+
+    @staticmethod
+    def format_result(prefix: str, data: dict) -> dict:
+        if data.get('type', None) != 'FeatureCollection' or not isinstance(data.get('features', None), list):
+            return dict()
+        features = data.get('features', [])
+        result = dict()
+        for f in features:
+            if (f.get('id', None) is None or
+                    f.get('properties', {}).get('value', None) is None or
+                    f.get('properties', {}).get('timestamp', None) is None):
+                continue
+
+            try:
+                timestamp = datetime.fromisoformat(f.get('properties', {}).get('timestamp'))
+                value = float(f.get('properties', {}).get('value'))
+            except (TypeError, ValueError):
+                continue
+
+            name = f"{prefix}:{f.get('id').split('.')[0]}"
+            if name not in result or result[name]['timestamp'] < timestamp:
+                result[name] = FeatureValue(timestamp=timestamp, value=value)
+
+        return result
+
+    async def _api_wrapper(self, url: str, querystring: dict):
+
+        headers = {'User-Agent': 'github.com/jdejaegh/python-irceline'}
+
+        try:
+            async with async_timeout.timeout(60):
+                response = await self._session.request(
+                    method='GET',
+                    url=url,
+                    params=querystring,
+                    headers=headers
+                )
+                response.raise_for_status()
+                return response
+
+        except asyncio.TimeoutError as exception:
+            raise IrcelineApiCommunicationError("Timeout error fetching information") from exception
+        except (aiohttp.ClientError, socket.gaierror) as exception:
+            raise IrcelineApiCommunicationError("Error fetching information") from exception
+        except Exception as exception:  # pylint: disable=broad-except
+            raise IrcelineApiError(f"Something really wrong happened! {exception}") from exception
diff --git a/src/open_irceline/data.py b/src/open_irceline/data.py
new file mode 100644
index 0000000..93533a2
--- /dev/null
+++ b/src/open_irceline/data.py
@@ -0,0 +1,27 @@
+from enum import StrEnum
+from typing import TypedDict
+from datetime import datetime
+
+
+class RioFeature(StrEnum):
+    BC_HMEAN = 'rio:bc_hmean'
+    BC_24HMEAN = 'rio:bc_24hmean'
+    BC_DMEAN = 'rio:bc_dmean'
+    NO2_HMEAN = 'rio:no2_hmean'
+    NO2_DMEAN = 'rio:no2_dmean'
+    O3_HMEAN = 'rio:o3_hmean'
+    O3_MAXHMEAN = 'rio:o3_maxhmean'
+    O3_8HMEAN = 'rio:o3_8hmean'
+    O3_MAX8HMEAN = 'rio:o3_max8hmean'
+    PM10_HMEAN = 'rio:pm10_hmean'
+    PM10_24HMEAN = 'rio:pm10_24hmean'
+    PM10_DMEAN = 'rio:pm10_dmean'
+    PM25_HMEAN = 'rio:pm25_hmean'
+    PM25_24HMEAN = 'rio:pm25_24hmean'
+    PM25_DMEAN = 'rio:pm25_dmean'
+    SO2_HMEAN = 'rio:so2_hmean'
+
+
+class FeatureValue(TypedDict):
+    timestamp: datetime | None
+    value: int | float | None
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29