How Clean Is the Air in Your Classroom? Your Theater? It’s Not Easy to Find Out

Photo-Illustration: by Curbed; Photo Getty Images

Architecture, declared Le Corbusier, is the “play of masses brought together in light.” That statement, made when photography and the art of building were defining each other’s frontiers, has wormed its way into our collective consciousness. We look at architecture and judge it by what we see. It’s harder to register how a building breathes, and not as sexy to examine the mostly invisible network of fans, compressors, dampers, windows, filters, vents, ducts, and switches that keep clean air — not too hot, not too cold, not too humid, not too dry — coursing through indoor spaces.

As students jostle into school buildings and Broadway theaters shudder back to life, the most obvious signs of a new hygienic alertness will be masks and vaccination cards. But we also have an invisible vector of anxiety. Outdoors, the air dissipates pathogens; indoors, it can pass them around. Fortunately, we have the technology to cleanse the air as it goes swirling through cafeterias, lobbies, and other crowded spaces. The problem is that the public can only guess how well the machinery is doing its job. Is that a teacher’s monotone making you drowsy or the buildup of your classmates’ carbon dioxide? Is a frosty room the sign of an efficient HVAC system or a hint that it’s recycling already-cooled air? Do we need to worry that the products of an intermission coughing fit may linger through the finale?

Throwing open doors to the public is an invitation to come in and pollute, and it is not purely a COVID concern. Yes, we have a specific and timely reason to be anxious about packing into one big room swathed in the moist, carbon-heavy vapors of our neighbors’ exhalations. But the truth is that those undetectable indoor clouds have always carried an unpleasant cargo. Any group of people huddled in the same space, whether the décor is steel and linoleum or red velvet and marble, will share flu and cold viruses. Bacillus and mold spores emanate from walls. The noxious chemicals used to create an illusion of cleanliness linger in the ducts. Our newfound preoccupation with indoor-air quality shouldn’t ebb as the pandemic recedes.

Making theaters, concert halls, and schools safe places to breathe isn’t an insurmountable challenge, but it does mean overcoming a history of terrible habits, widespread neglect, scant standards, and zero transparency. “Our clients are really paying attention now, and they’re finding some things that nobody ever thought about,” says Charles Copeland, a longtime engineer who has made something of a specialty of modernizing creaky theaters and concert halls. All over the city, facilities managers are rushing to tune up clanky old air conditioners. The Department of Education is conducting classroom-by-classroom surveys of airflow, not always with happy results. Suddenly, ventilation engineers are in high demand as building owners are desperate to make up for decades of neglect.

We need these spasms of panicked attention because the systems that technicians are being called in to fix were never supposed to be noticed. We don’t generally fill our lungs in a school cafeteria and exclaim at the freshness of the scent or bask in the pleasant breeze wafting through an office hallway. The only time most of us think about indoor air is when it’s putrid or stale. That obliviousness can extend to real-estate owners and managers, who often spend millions on an HVAC system and then ignore it for years. Dampers are left shut. Windows rust. Filters fail and go unreplaced. The cost of an overhaul mounts and gets indefinitely postponed. Off–Off Broadway companies operate on the scrawniest budgets, which don’t usually include fancy climate control. A regular theatergoer I know refers to the balcony in one of her least favorite downtown venues as a “dank horror show.”

Schools and performance halls have overlapping issues but vastly different circumstances. Each classroom is a microclimate, which means that a simple box fan with a HEPA filter can do wonders for the local atmosphere, but a whole school building is a study in complexity and unpredictability. Cracking open a window might fill a classroom with bracing winter air, but it could also scramble calibrated air currents or trigger a thermostat, causing a neighboring room to overheat. Letting nature in also makes it impossible to take standard measurements like the number of air changes per hour. Modern ventilation systems come with monitors and automated controls, which adjust the settings depending on, say, outside temperature and how many people are in the building. But usually, reading a room’s air flow is like taking a patient’s blood pressure: a snapshot of constantly changing conditions.

Standards are low and meeting them is effectively optional. There is no inspection system for air quality as there is for, say, elevator cables and food safety in restaurants. Building managers can announce all the measures they’re taking without quantifying their effects. “If it’s just meeting code, that’s not sufficient, but no one has set firm ventilation targets,” says the Harvard healthy-buildings expert Joseph Allen. “ASHRAE [the ventilation industry’s trade association] and the CDC say: Bring in more outdoor air. The obvious question is: How much?” The ambiguity leaves building owners to improvise and guess. The nonprofit organization Ars Nova is using ionization technology and portable air filters at its 199-seat theater on Barrow Street to supplement an HVAC system that, despite a recent upgrade, neither vents to nor draws any air from the outdoors. “I’m not a doctor; I make theater,” says executive director Renée Blinkwolt. “But I’ve followed the advice of experts, and they’re telling us that this is the best we can do.”

Large theaters and concert halls operate on a different order of magnitude from schools. The exhalations of several thousand immobilized people waft toward a high ceiling, where the warmed, carbon-and-germ-laden miasma is sucked into ducts and passed through ultra-fine MERV 13 filters or —when the system’s on the fritz or merely underpowered — hovers there, eddying around the cheap seats. One venue contains a multitude of spaces, each with its own social and airflow dynamics. The Metropolitan Opera has a cavernous auditorium, but in the half hour before curtain, the line to pick up tickets snakes through a jammed lobby. Theatergoers are — or were — inured to the crush of intermission, when heading for the bathroom often means waiting in a narrow stairwell that leads to the basement. Over the course of the evening, the air gets soupier, and those seated in the balcony breathe in the concentrated fumes from below.

Many Broadway theaters date from the Gilded Age, and they have the narrow stairwells, negligible legroom, and tight seats to show for it, along with backstage areas that make vole dens seem spacious and sanitary. The discount ticket broker NYTIX’s website has a theater-by-theater description of the audience experience, and the Belasco comes in for some especially dyspeptic commentary: “If smoke is used in the show, it will linger in the balcony for quite a long time as the ventilation system is wholly inadequate and often feels akin to the old days that allowed cigarette smoking in the theatres.” (The Shubert Organization, which owns the Belasco, declined to elaborate on upgrades to ventilation in its theaters.)

Performers and crew members have an even greater interest in the safety of the air they work in than audiences do. During the pandemic, Actors’ Equity began demanding that theater owners hire ventilation professionals to inspect and, if necessary, overhaul their air-handling systems. That has the dual benefit of protecting its members and instilling confidence in a skittish audience. “I feel pretty comfortable that the air I’m going to breathe in any theater this fall is going to be safer and cleaner than in the same theater in March of 2020,” says Andrea Hoeschen, the union’s in-house lawyer. That’s a low bar, of course, and whether the same claim will still be true a in few years is anybody’s guess.

For now, most venues are, publicly at least, more focused on getting audiences to comply with masking and vaccine requirements than on spelling out the ways they have improved their facilities. There is no grade system to let the public know how safe it is to breathe, no regimen of inspections, and no one to verify that standards, once in place, get maintained. Until recently, we’ve always taken it on trust that the air in public buildings is free, or at least free-ish, of spores, particulates, toxins, and viruses, because we thought we had no choice. The pandemic has made it clear that the trust was misplaced and laxity can be dangerous.

How’s the Air in Theaters? Classrooms? It’s Hard to Find Out