diff --git a/CHANGELOG b/CHANGELOG
index 44862577f1883a32bdf965cb9fc8f62950fef4d1..0d7628575f045120e7ffb1a4ca92c76ef21dc899 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -13,3 +13,7 @@
 ## 0.0.3 - 2025/05/20
 
 - Adding remove countries functionality that we can Remove the data of Countries we deem to be wrong
+
+## 0.0.4 - 2025/06/25
+
+- Update unit change re CO from milligrams to micrograms
diff --git a/setup.py b/setup.py
index 156ee30e48d1dbab4df943b9f57849c2a7b17964..e90336153ca028a242e1fab1cad3947bd67f0448 100644
--- a/setup.py
+++ b/setup.py
@@ -10,7 +10,7 @@ from setuptools import find_packages
 from setuptools import setup
 
 # Could update this using versioneer
-version="0.0.3"
+version="0.0.4"
 
 setup(
     name="monarch-DA-preprocessor",
diff --git a/src/in-situ/unit_change_re b/src/in-situ/unit_change_re
index b617d35f9d81910e987ae70c45dc2f6200f2fcf6..9fef2e0054cddb8bff766435ea77faae31fa40b2 100755
--- a/src/in-situ/unit_change_re
+++ b/src/in-situ/unit_change_re
@@ -1,6 +1,6 @@
 O3 1./1995.7
 NO2 1./1912.5
 SO2 1./2661.
-CO 1./1.164
+CO 1./1164.
 PM10 1e-3
 PM25 1e-3