Legendary Italian horror director Mario Bava assisted with the making of the special effects on this film. Bava passed away shortly before its release.
For some of the exterior location shoots in Italy footage of New York City skyscrapers were superimposed in the background to make it appear like the films NYC setting.
In an interview with assistant director Lamberto Bava, he said that he handled and wrangled so many cats during the shooting of this film that afterward he could no longer stand to be in the same room as a cat. He's avoided them since then.
Argento said that the gentleman who provided the live ants used in the film collected them by walking around in the park with a vacuum and literally sucking them up from the ground. He would later retrieve them from the vacuum bag once on set.
Part of the reason Argento cast Irene Miracle as Rose Elliot was she had synchronize swimming skills, which came in quite handy for the shooting of the underwater ballroom scene.
According to co-writer and star Daria Nicolodi she didn't fight for writing credits on this film as she had an ordeal just getting writing credit on Argento's previous film Suspiria. According to Nicolodi the basic plot of 'Inferno' was her creation.
When star 'Leigh McCloskey''s stunt double broke his leg, McCloskey himself had to perform the stunt work for the films explosive finale. In interviews McCloskey said it was an intense experience as the rest of the crew and equipment were protected by multiple layers of Plexiglas while he had to run without protection through sets rigged to explode and burn. McCloskey said 'when you feel glass flying by you like a Harrier jet, you never forget it!'
According to 'Leigh McCloskey', Dario Argento's brother Claudio Argento spoke better English than Dario so often he would have to translate Dario's direction to the cast.
Reportedly Dario Argento was ill with a serve case of hepatitis through out the production. At one point he had to be bed-ridden for a few days leaving the production to work on only second unit. Argento has since called 'Inferno' perhaps his most challenging film for this reason alone.
For the scene where Kazanian carries the bag of 'cats' into Central Park a mechanical device was placed inside the bag to make it move, giving the impression that there were actually live animals inside.
Mario Bava is credited with creating the design of Rose Elliot's unique apartment building. Bava also built the small-scale model that was burned in the films fiery climax.
The trivia items below may give away important plot points.
In Kazanian's bizarre murder scene, it appears that the knife-wielding hot dog vendor runs across the pond to him. A Plexiglas bridge was placed just under the surface of the pond to make it appear that the vendor runs across the water guided by supernatural forces.