diff --git a/caimira/models.py b/caimira/models.py
index 756f62d1..4559809b 100644
--- a/caimira/models.py
+++ b/caimira/models.py
@@ -1432,7 +1432,7 @@ class ExposureModel:
         return (CO2_conc_limit * (1 - fac) + (co2_conc_at_last_state_change - 0.0004) * fac) + 0.0004
 
     def CO2_concentration(self, time: float) -> _VectorisedFloat:
-        return max(440, self._CO2_concentration(time) * 10**6)
+        return self._CO2_concentration(time) * 10**6
 
     def long_range_deposited_exposure_between_bounds(self, time1: float, time2: float) -> _VectorisedFloat:
         deposited_exposure = 0.
diff --git a/caimira/monte_carlo/data.py b/caimira/monte_carlo/data.py
index e0eaa09a..35dc3eb4 100644
--- a/caimira/monte_carlo/data.py
+++ b/caimira/monte_carlo/data.py
@@ -86,6 +86,14 @@ activity_distributions = {
 }
 
 
+co2_activity = {
+    'Sleep': mc.Activity(0.013, 0.013),
+    'Resting': mc.Activity(0.02, 0.02),
+    'Normal work': mc.Activity(LogNormal(0.08, 0.13), LogNormal(0.08, 0.13)),
+    'Hard work': mc.Activity(LogNormal(0.33, 0.38), LogNormal(0.33, 0.38)),
+}
+
+
 # From https://doi.org/10.1101/2021.10.14.21264988 and references therein
 symptomatic_vl_frequencies = LogCustomKernel(
     np.array((2.46032, 2.67431, 2.85434, 3.06155, 3.25856, 3.47256, 3.66957, 3.85979, 4.09927, 4.27081,