The Republican National Convention this week takes place under a certain sense of unease, and not just of the norovirus variety. Recent attacks in Nice and Dallas are just the most recent in a string of violent events that make the world feel off-kilter, and large gatherings of people like a potential target.

The city of Cleveland is prepared, of course, though even its police officers are uneasy about the city’s generous open carry laws this week, which allow for powerful weapons to be carried outside the convention’s home at the Quicken Loans Arena. There’s another kind of threat, though, that Cleveland has also readied itself for: That of a biological, chemical, or radiological event.

First Off: Unconventional Attacks Are Very Rare

There’s no joy in being alarmist, so best to say this upfront: The chances of a biological or chemical agent, or radiation from an dirty bomb, are slim. The United States hasn’t experienced anything remotely comparable since the anthrax scares that immediately followed the September 11 attacks. Prior to that, outside of active warfare, there is only one other example to point to in the past two decades: a coordinated sarin attack terrorized the Tokyo subway system in 1995, killing 13 people and sickening thousands more.

Both of those incidents were terrible. But that there are so few to point to is more than just a happy accident. A multitude of factors have helped prevent unconventional attacks over the last decade and beyond, starting with good old fashioned spy work.

“The best way to preempt these things is solid intelligence,” says Kyle Olson, founder of the Olson Group, a company that provides emergency management and homeland security services to the US. “I think it’s fair to say that our intelligence capability today… is better than it’s been at any time in our history. If there’s any chatter about an organized attack, we’re probably going to pick that up.”

That distinction about an organized attack is important–an attack of the “lone wolf” variety is much harder to plan for. The good news is that though chemical, biological, and radiological attacks may not take quite as much sophistication as you’d think, they likely require more coordination than other terrorist methods—especially to be maximally impactful.

“A weapon of mass destruction, like a chemical or radiological or biological weapon, those are weapons that tend to appeal to an organized force than to an individual,” says Olson. “An individual, for want of a better way of putting it, is going to get more satisfaction from something that goes bang.” Which, more than even top-shelf surveillance, may be the best explanation for why we haven’t seen unconventional attacks in the United States. It’s not that people don’t mean to do harm; it’s that there are more efficient, affordable, impactful ways to do it.

“There are much easier ways to kill people, or injure them,” says Dr. Eric Toner, Senior Associate at the UPMC Center for Health Security, who specializes in catastrophic event preparedness. “Why go to the trouble of putting together a chemical or biological weapon when you can do the same thing with an assault rifle, or a fertilizer bomb?” (Okay, so, maybe it’s worth being a little alarmist. It’s just a different kind of alarm.)

Still, the Cleveland Police are preparing for every scenario, even the rarest variety. They the City of Cleveland did not respond to WIRED's request for comment, experts and public records reveal how.

Police officers in Cleveland, Ohio demonstrate some of their security assets, including remote-controlled robots, horse-mounted officers, bomb-sniffing dogs on July 14 2016 ahead of the Republican National Convention.

The city, in conjunction with federal agencies, is boosting security for the high-profile event. / AFP / Michael Mathes (Photo credit should read MICHAEL MATHES/AFP/Getty Images) Police officers in Cleveland, Ohio demonstrate some of their security assets, including remote-controlled robots, horse-mounted officers, and bomb-sniffing dogs, on July 14, 2016.AFP/Getty Images

An Ounce of Prevention

If someone (or, more likely, some group) were to sneak a significant quantity of biological or chemical agent into downtown Cleveland, systems are in place to identify and contain the risk.

First, there’s the sheer manpower. Department of Homeland Security pointed WIRED to comments by Secretary Jeh Johnson, who testified before Congress recently that DHS would has 3,000 personnel on-site, a group that comprises Secret Service, TSA, Homeland Security Investigations, ICE, the National Protections and Program Directorate (NPPD), and the Coast Guard. They are joined by another thousand US government personnel, along with “thousands” of state and local law enforcement officials. It’s quite a crew.

“Events like this are designated National Special Security Events,” says Olson. “Because it’s an NSSE, it’s able to tap into the resources of the FBI, and special intelligence assessments from the intelligence community. They’re able to tap into military security assets. And every city has at least one civil support team, which is a chem/bio/radiological specialized team within the National Guard.”

Those teams are likely positioned, Olson says, if not directly inside the convention arena then at most a block away.

The human assets are augmented by technological ones. DHS has Mobile Detection Deployment Units on hand, trailers that contain radiation detection gear for dozens of emergency responders. The specific equipment ranges from backpack radiation detection units, handheld instruments, and tracking gadgets. There are also technicians standing by to assist local authorities master all the complexities of the unfamiliar equipment.

DHS is further supporting Cleveland through its BioWatch program, a system that originated after the anthrax attacks of 2001. In theory, BioWatch works by sampling the air at positions around major US cities, both on top of buildings in busy areas and at sensitive locations like airports and subways. That’s a little less comforting, though, given that BioWatch samples can take well over a day to yield a result, and that after years of false positives, the GAO questioned its efficacy just last November.

Slow and possibly wrong is still better than no detection at all. Besides which, these are only the detection apparatuses we know about.

“There are going to be several trailer-loads of specialized equipment that most of us are not even aware exists,” says Olson. “There’s an entire little science-fiction army operating in the background.”

A unit of the California Highway Patrol enter Public Square in downtown Cleveland with riot gear and tear gas rifles on July 19, 2016. Michael Robinson Chavez/The Washington Post/Getty Images

The Response

But what if, despite all that diligence and the relative unlikelihood, a chemical, biological, or nuclear incident were to happen? Not surprisingly, it depends.

“For an event like the RNC, where there’s time to prepare, there’s a lot that can be done to lessen the impact of the attack,” says Toner. Credit for that preparedness goes, at least in part, back to the anthrax attacks of 2001. He explains that cities and hospitals have been working on this for the last 15 years, holding trainings and stocking up on specialized equipment.

In the case of a chemical event, which could impact hundreds of people instantaneously, priorities would be on treating the victims and decontaminating the area. Another thing all agencies and communities factor in is that the use of a biological agent, Toner says, likely wouldn’t register for several days, at which point various dispersed delegates and protestors would begin getting ill.

Again, this specific form of terror seems less likely than those that have seemed constantly to disrupt the world over the last several months an years: namely, violence enacted with guns or bombs. But unlikely doesn’t mean impossible, especially given that the primary deterrent to this kind of attack seems to be that other methods of tragedy are more easily achieved.

“As we’ve seen again and again, over the last few weeks and months, the unthinkable happens every day now,” says Olson. As he puts it: It's not a matter of if, but when.