Life safety practice questions

Screen doors and storm doors are the only doors excepted from the rule against a door swinging over steps. The egress door gets no exemption: its one exterior step is allowed only where the door swings clear of it. Wherever a riser drops to the exterior landing, the door swings to the interior.

A photoelectric alarm shines a light above a sensor set at 90 degrees to the beam, so the sensor sees no light until smoke scatters some of it toward the sensor. A beam aimed straight at the sensor is not the arrangement used. Radioactive material and a current between two sensors describe the ionization alarm.

Because a button press may skip the sensor, a sounding alarm does not show that it will work as intended in an actual fire or carbon monoxide event. A home inspector who tests alarms and reports the results should explain that distinction to the client. Reporting the alarms as confirmed working claims more than the test can show.

Carbon monoxide alarms last around five to seven years, a shorter service life than smoke alarms have. The figure of about ten years is what many smoke alarm makers give for replacing a smoke alarm, so it does not describe the carbon monoxide alarm.

Smoke alarms should be kept away from combustion sources such as garages and from fuel-burning equipment like a boiler, furnace, fireplace, or water heater, and some makers recommend 20 feet or more of separation. Ten feet is the range clearance for an ionization alarm with a silence switch, which is a different rule.

An ionization alarm with no silence switch belongs 20 feet or more from the range, so 12 feet is too close. The 10 foot figure applies only when the ionization alarm has a silence switch, and the 6 foot figure applies to a photoelectric alarm.

The placement limits for carbon monoxide alarms resemble the smoke alarm limits without matching them exactly, and the kitchen restriction is one that carries over. The combustion source, high humidity, fan and operable window, and 4 inch dead air restrictions carry over too. The 12 inch limit below the ceiling is the one that does not.

OSB and plywood qualify as fireblocking at 23/32 inch thick, which is nominally 3/4 inch. The 1/2 inch figure belongs to drywall used as fireblocking, not to wood panels.

Without a parapet, the roof covering over a townhouse firewall should be non-combustible, with fiberglass shingles as one example, and 5/8 inch Type X drywall should line the sheathing from below, 4 feet or more each way from the firewall. A firewall that reaches the sheathing is the baseline, and the roof treatment is still needed on top of it.

The standards line gives R302.11 for fireblocking. R302.5 covers fire separation in the garage, R302.3 covers two-family dwellings, and R302.2 covers townhouses.