diff --git a/opensensor/collection_apis.py b/opensensor/collection_apis.py
index 5e56042..4bd9a4c 100644
--- a/opensensor/collection_apis.py
+++ b/opensensor/collection_apis.py
@@ -457,7 +457,7 @@ async def record_environment(
 ):
     db = get_open_sensor_db()
 
-    # TODO - Refactor this after migration to FreeTier complete
+    # Paid customers may have their own collection
     if user:
         collection_name = user.collection_name
     else:
diff --git a/opensensor/collections.py b/opensensor/collections.py
index 0fad60d..43cf688 100644
--- a/opensensor/collections.py
+++ b/opensensor/collections.py
@@ -1,9 +1,9 @@
 import json
 from datetime import datetime
 from decimal import Decimal
-from typing import List
+from typing import List, Optional
 
-from pydantic import BaseModel, validator
+from pydantic import BaseModel, Field, validator
 
 
 class TimestampModel(BaseModel):
@@ -74,5 +74,5 @@ class VPD(BaseModel):
     """
 
     timestamp: datetime
-    vpd: float
+    vpd: Optional[float] = Field(None, description="The computed VPD value.")
     unit: str