Ventilation Crawling

Lore & Background

In HVAC systems, ducts can be made of galvanized steel, which is the standard and most common material because the zinc coating prevents rusting and avoids cost of painting. Metal ducts are typically lined with faced fiberglass blankets (duct liner) or wrapped externally with fiberglass blankets (duct wrap). When necessary, a double walled duct is used, usually with an inner perforated liner, then a 1–2 in (2.5–5.1 cm) layer of fiberglass insulation contained inside an outer solid pipe. Rectangular ductwork commonly is fabricated to suit by specialized metal shops, most often coming in 4 ft (120 cm) sections. Round duct is made using a continuous spiral forming machine, with stock sizes ranging evenly from 4 to 24 in (10 to 61 cm), with 6–12 in (15–30 cm) being most commonly used. Flexible ducts are typically made of flexible plastic over a metal wire coil to shape a tube, with insulation usually being glass wool in the United States, or both polyester fiber and glass wool in Australia. Flexible duct is very convenient for attaching supply air outlets to rigid ductwork, but the pressure loss is higher than for most other types of ducts. Designers and installers attempt to keep installed lengths short, e.g. less than 15 feet (4.6 m) or so, and try to minimize turns. Kinks in flexible ducting must be avoided.

In Their Own Story

The metal grate groaned softly under his weight as he pulled himself inside, the air instantly tasting of dust and stale ozone. He pressed his back against the cold wall, holding his breath as a spotlight swept across the corridor below. Inside the duct, every movement felt amplified; the scrape of his boot against the floor echoed like thunder in his ears. He crawled forward on elbows and knees, inching past the hum of a distant fan, knowing that one wrong move would seal his fate before he ever reached the control room.

Reader's Guide

To execute ventilation crawling effectively, players must first locate an accessible vent cover, often requiring a lockpick or specific tool. Once inside, movement speed is significantly reduced compared to normal running, demanding patience and careful navigation. In many titles, cameras or guards can hear noise generated by rapid movement within ducts. Players should move slowly or hold their breath to minimize sound profiles. Some games introduce fans that deal damage if the player moves too quickly; these must be timed carefully or avoided entirely. Puzzles often involve switching between different vent paths or removing obstructions like debris or locked grates from the inside. Always check for alternative exits, as some ducts lead to dead ends or trap rooms designed to flush out intruders.

Did You Know?

• Galvanized mild steel is the standard and most common material used in fabricating ductwork because the zinc coating prevents rusting and avoids cost of painting.
• Round duct is made using a continuous spiral forming machine which can make round duct in nearly any diameter when using the right forming die and to any length to suit.
• Flexible ducts are typically made of flexible plastic over a metal wire coil to shape a tube, and in the United States the insulation is usually glass wool.
• The UL181 test requires a negative pressure of 200 Pa for flexible ducting.
• Fabric ducts are not rated for use in ceilings or concealed attic spaces, but products for use in raised floor applications are available.