Advise me good online stores to purchase it.
Fire alarm is very important and I do not advise you to buy it in online stores. You can get a bad Chinese fake and it can be dangerous for your life! Better to turn to professionals. I constantly appeal to this company https://www.americanbackflowprevention.com/service-backflow-testing.php that is cross trained in all aspects of plumbing, fire sprinklers, and fire alarms. Thanks to their services, I am sure that my life will be safe