Fenced off or set back from streets and sidewalks and often raised on platforms as well, civic monuments are oddly ideal candidates for concealing a peculiar secondary function: the ventilation of subterranean spaces, from sewage systems to subway tunnels.

In Sydney, Australia, the Hyde Park Obelisk was built precisely for this purpose back in 1857. Modeled on Cleopatra’s Needle located on the banks of London’s River Thames, the 60-foot-tall tower was designed to allow noxious gases to escape upward from the sewers below. Today, the monument remains in place, but vents the city’s somewhat-less-smelly stormwater system instead.

Meanwhile, in Nuremberg, Germany, a controversial set of statues depicting the trials of married life was commissioned specifically to disguise the subway exhaust port located on the site.

The Ehekarussell (roughly translated: marriage-go-round) is critiqued not because of noxious fumes, but for featuring a sequence of scenes through its statuary: a young happy couple turning older and angrier before one spouse slays the other.

Another approach that appears in many cities is more architectural, though no less monumental, using anything from small fake shell houses to huge multistory buildings as giant exhaust conduits.

In Burnaby, British Columbia, a boxy little house serves both to vent subway fumes but also acts as a mid-tunnel escape route for emergencies. Many of these structures not only act as exhaust pipes, but also contain bacterium-based odour removal plants so as to spew somewhat less obnoxious gasses.

The Callahan Tunnel ventilation building in Boston is a relatively less-camouflaged and more-imposing affair built of bricks with vents where one would ordinarily expect to see windows. Many other American cities have similarly larger exhaust buildings, including New York City, where they vent infrastructure including the Holland Tunnel.

Typical art travels inside, safely stowed in carefully-packed containers to prevent damage – these drawings do the opposite, playing up the folk-artsy practice of scribbling into built-up grime on vehicles.

“Using his finger to scribe into the layer of dirt built-up from exhaust emissions,” Ben Long “creates elaborate drawings on the rear shutters of white haulage trucks. In this on-going series, collectively entitled The Great Travelling Art Exhibition, he expands upon the daubing and crude slogans that commonly adorn commercial freight vehicles.”

Some of the pieces will be rapidly wiped away by rain or vandals, but others have survived for as long as six months and on long cross-country road-trips made by their drivers. Like street art, these reverse graffiti works are susceptible to the elements and necessarily temporary.

The artist’s motivations are various, but include a desire to make his work more accessible outside of traditional gallery spaces, reduce the costs of creative expression by using free materials and obviating the need for a studio space in which to create.

At the same time, there are a lot of artistic conventions still in play here – hallmarks of the ‘high art’ world, as it were. Long crafts these compositions within (and with reference to) a fixed frame, much like a canvass, and signs the pieces as well.