Try this bit of SQL in your Database Manager to help identify what you're looking for (in my case Temperature). It should match what you're seeing from the Environmental Monitors:
SELECT hi.DisplayName, hi.Value, hu.HtmlText, hi.NodeID
FROM APM_HardwareItem hi
INNER JOIN APM_HardwareUnit hu
ON hi.Unit = hu.ID
WHERE hi.IsDeleted = 0
AND hi.HasHistoricalData = 1
AND hi.NodeID = 22 -- <-- Insert the Node ID here to see all available data for that device<--
Then you can refine the query until you get just the Value field, from which you can create an SQL alert condition.