Difficult to predict, asynchronous errors are generally due to a failure on the part of the operating system. By far the most common example is "out of memory." Other asynchronous errors are failure to open a file, perhaps due to lack of disk space, or hardware failure.

The usual response to these types of errors by the Essential Math Module is to throw an exception. If exceptions are not available, the default error handler posts a note to standard output with the type of error, then aborts the program. This default handler can be changed.