A powerful tornado hit across St. 香港三级片 Friday afternoon, leaving five people dead, dozens with injuries, buildings leveled and walls ripped away and tens of thousands of people without power.
Soon afterward, residents said the EF-3 tornado had caught them by surprise. They hadn鈥檛 heard any warning sirens, they said.
On Saturday, city officials said the sirens may not have worked as they should have 鈥 something they later confirmed 鈥 but that sirens are intended to warn people outdoors that they should go inside, rather than notify people already indoors.
And in the digital age, where emergency notifications can automatically alert on cellphones, some are asking if a manually activated siren system is outdated.
Locally, Sentry Siren has systems in Wright City, Missouri, Okawville, Illinois, and Evansville, Indiana. American Signal Corp. has systems in Missouri鈥檚 Holt and Macon counties. ATI Systems does the sirens for Jefferson County in Missouri and St. Clair County in Illinois.
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St. 香港三级片 has 60 outdoor sirens and St. 香港三级片 County has 204, from Whelen Engineering Co., of Connecticut.
Siren experts Evan Kerr, the national sales manager at Colorado-based Sentry Siren Inc., Justin Raff, a regional sales manager at Wisconsin-based American Signal Corporation and Bob McLaughlin, manager at Boston-based ATI Systems, explained how the systems work:
Should I be able to hear tornado/outdoor warning sirens indoors?
You might be able to hear sirens from inside your home, but sirens are built to be heard outside, Raff said.
鈥淭hey鈥檙e made for public spaces. They鈥檙e not meant for indoor notification. That鈥檚 a weather radio or TV,鈥 he said. 鈥(Outdoor) sirens are to let you know that something is going on and to check your cell phone.鈥
And there are too many variables (a building鈥檚 construction, kind of insulation and type of windows) for manufacturers to guarantee their sirens can reach people indoors, Kerr said.
鈥淲e can only build them so loud,鈥 Kerr said. 鈥淚t could get to the point where we could actually be causing hearing damage for people under the sirens.鈥
How far can a siren be heard?
It depends on how many large buildings are in the area, which way the siren is facing, local topography, foliage and even humidity, Raff said. Typically, a siren鈥檚 alert can reach 1 to 2 miles, but siren sites should be built closer to each other than that, he said.
鈥淩edundancy is key,鈥 Raff said. 鈥淵ou鈥檙e always going to want some overlapping. You鈥檒l hear 鈥榣ess is more鈥 when it comes to sirens. That鈥檚 not true.鈥
Kerr said Sentry Siren鈥檚 most popular model, the 14V-B, is 127 decibels and can cover roughly a 1-mile radius. The louder models, which are over 130 decibels, can be heard up to 1.2 miles away.
How far apart should one siren be placed from another?
The Federal Emergency Management Agency (FEMA) has guidelines on outdoor warning systems and recommendations based on the siren鈥檚 sound frequency, ambient noise, structural barriers and more.
But Kerr said the local emergency manager is typically the person who makes that decision, balancing available funds with optimal siren placement.
Kerr said sometimes communities will buy a few sirens annually rather than all at once, to accommodate a municipal budget.
鈥淚n many cases, it鈥檚 an elected council and it鈥檚 up to them to decide what鈥檚 most important,鈥 Kerr said. 鈥淪ometimes it鈥檚 the case that [sirens] are not the important thing.鈥
Are there different types of siren models? Can the volume be changed?
Siren features depend on a buyer鈥檚 needs. Some are solar-powered, while others are battery-powered. They can be rotating, omni-directional or directional. The two main types are mechanical sirens and electronic sirens.
Kerr said he recommends mechanical sirens as they have a longer lifespan and are more dependable.
Mechanical sirens contain a fast-spinning fan that creates sound. Electronic sirens emit electronically-created noise, so the volume can be changed to be louder or softer, like on a television.
鈥淚f the electricity goes out, these things can keep operating for seven days,鈥 McLaughlin said. 鈥淎ll you need are your ears. 鈥 We work when nothing does.鈥
What is the lifespan of an outdoor warning siren system?
Systems can last up to 20 years, according to McLaughlin. So at 25 years old, St. 香港三级片鈥 emergency siren system is in need of replacement, he said.
St. 香港三级片 has allocated toward a replacement system. In 2012, St. 香港三级片 County activated a new outdoor warning system that cost $7.5 million.
Why is St. 香港三级片 City more dense with sirens than St. 香港三级片 County?
Raff, of American Signal Corporation, said the city has more tall buildings and more population density than the county.
鈥淲ith various structures, penetration of sound is just not the same. You want more sirens to be heard,鈥 Raff said. 鈥淥ther cities are like this. This is not unique to St. 香港三级片 itself.鈥
Kerr said they 鈥渄efinitely鈥 take the population of a place into consideration when mapping out a siren system.
鈥淲hat can we best do to alert the most people?鈥 he said. 鈥淲here are most people going to be outside to hear these? Where will someone be away from their phone?鈥
McLaughlin said an industry rule of thumb is to cover any area that has 2,000 citizens per square mile for rural areas. ATI Systems is currently working on erecting sirens in unincorporated Jefferson County.
McLaughlin said the local government originally wanted sirens to cover the whole area, but after ATI Systems created an acoustic map of the area based on the 2,000 people per square mile rate, the company was able to cut down the number of sirens needed.
How big of an investment are sirens for a community?
Pretty big. Raff said the installation of a single siren site could cost up to $30,000. Many towns and communities have over 130 sirens, with annual maintenance running up to $700 per siren.
Raff said it鈥檚 not uncommon for cities or municipalities to get grant funding to help pay for sirens, but recently some federal grants have paused by the Trump Administration.
McLaughlin said a drop in FEMA funds led ATI Systems to see fewer orders scheduled for 2026, but that鈥檚 a 鈥渟peed bump not a major dip,鈥 as he anticipates the money to be reinstated.
But some communities are opting to not invest in sirens at all and solely rely on emergency weather notifications sent to cell phones, both Raff and Kerr said. But that could be dangerous.
鈥淚t shouldn鈥檛 be your only tool,鈥 Kerr said. 鈥淭here isn鈥檛 yet a perfect tool to alert everyone all at once. We have to put all the tools we have available to use.鈥
St. 香港三级片 Mayor Cara Spencer on Wednesday, May 21, describes leaders' response to the failure to activate the emergency warning system on May 16, 2025. Video edited by Beth O'Malley
