I can tell you what Microsoft provides for this requirement, not a warning kind of solution but kind of monitoring.
On the released products, you can define the material as hazardous material, and in the reporting details..
Here you can define the Hazardous stock limit and warning limit. Update quantities button is there which updates the on-hand quantity in this form.
To monitor all the hazardous material stock which are exceeding the stock limit, navigate as shown below:
Here i have put a filter with matches in Total Available as ((InventSum.AvailOrdered > PdsMRCItemDetails.HMIMWarningLimit)) and saved the view.
Filteration done in Advanced Filter
The view is added to a workspace also.
This is home page from where we can monitor, whenever we will login, all such cases can be seen easily.
You can also set some custom alerts if required.
Regards,
Neeraj Kumar