What must be installed around a type "B" vent that passes through a ceiling or floor as a safety measure?

A fire-stop must be installed around a type "B" vent that passes through a ceiling or floor to ensure safety and compliance with building codes. This is crucial because a fire-stop acts as a barrier to prevent the spread of fire and smoke between different areas of a building. Type "B" vents are designed for venting gas appliances and operate at higher temperatures; therefore, the installation of a fire-stop is necessary to protect combustible materials in the ceiling or floor structure from potential ignition due to the heat from the venting system.

The other options, while related to venting systems, do not directly address the critical safety needs associated with passing through ceilings or floors. A heat shield is not primarily used around vents to prevent fire spread, an insulation sleeve is typically used for thermal protection rather than fire safety, and a vent cap is meant to prevent rain and debris from entering the vent but does not serve a fire-stopping function. Thus, the requirement for a fire-stop is essential to maintaining safety standards in vent installation.