1552516 records to be exact? (1246 * 1246) That's what a Cartesian query does. Just thought I'd add something to the explanation of that.
Poor performance now?
This can be one reason: [EMSConDate] & " " & [EMSConTime]
Not only are you still concatenating fields, you're comparing the concatenation to Nulls...
([EMSConDate] & " " & [EMSConTime]) Is Not Null
As was already mentioned, concatenate in forms/reports, especially if the query performance is not good, and don't check concatenations with spaces for being Null.
Also test for better performance if you index any unique table fields (in design view).
Not sure why you've split date and time anyway? Why isn't it one field?
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.