Apocalyptic-sounding sirens will ring out over the east end of Toronto this week, but while it may sound like something out of a warzone or a blockbuster action flick, the jarring warning Scarborough residents can expect to hear on Wednesday is no cause for concern.

If you live, work, or attend school in the Guildwood or Rouge Park areas of Scarborough, it's going to get real loud on October 20, but it's all just a precaution to keep the area safe in the unlikely event of a chemical emergency.

Toronto East Community Awareness and Emergency Response (TE CAER) will be testing its community siren yet again on Wednesday at 2.05 p.m., part of a safety system that has already brought the decibels to unthinkable levels during previous tests.

The siren will make a "whoop, whoop" tone for two minutes, expected to travel for upwards of one kilometre in every direction, depending on weather conditions.

And we promise it won't be as good of a listen as the KRS-One hit that description immediately brings to mind.

After a sound that definitely is not that of the police, Scarborough will bask in five minutes of silence before a one-minute, monotone "all clear" tone ends the eight-minute test of both the siren and everyone's patience.

But instead of reaching for noise-cancelling headphones, you should probably take note of the test's distinctive sound. That "whoop, whoop" is exactly the warning you'd hear during a chemical incident.

Suppose that sound was to ring out anywhere outside of the stated testing period. In that case, people are instructed to immediately take shelter indoors, turn off ventilation systems that can draw air inside, and close all doors and windows. This is what your ears have been training for.

These neighbourhoods are among Toronto's closest to the sometimes-menacing Pickering Nuclear Generating Station, but the sirens are actually in place to warn of a much more local threat.

The Guildwood and Rouge Park neighbourhoods bookend an area of Scarborough home to a handful of chemical processing facilities, including complexes owned by Dow Chemical and Lanxess.

Chemical leaks from any of the facilities in this pocket of industrial land could threaten large swathes of surrounding areas, so preparedness is key for these communities.

Wednesday's test will be the last of 2021's provincially-mandated system checkups, but those living near the siren can expect more brain-rattling noise as testing is set to resume in the first few months of 2022.