Code Stories · why the rule exists
Gas: Sidewall Vent Terminals and Massachusetts CO Rules (Nicole's Law; 248 CMR 5.09(7) and 5.12(6))
The rule in Massachusetts today
Verbatim, 5.12(6): "12.9.7 Signage. Whenever any through-the-wall vent is installed less than seven feet above the finished grade, a metal or plastic identification plate shall be permanently mounted to the exterior of the building at a minimum height of eight feet above grade directly in line with the exhaust vent terminal. The sign shall read, in print size no less than 0.5 inches in size, "GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS"." 5.09(7): "9.1.23 Carbon Monoxide Protection. No installation or replacement of a vented gas appliance shall be permitted unless a battery powered or electrically hard wired carbon monoxide detector is present on the same floor as the appliance or on the next adjacent floor when the appliance is located in a crawl space unless the appliance is located in a detached, uninhabitable garage. For all residential dwellings, a carbon monoxide detector must also be present on each habitable level of the dwelling." Current 248 CMR 5.08 (eff. 12/5/2014) amends NFPA 54 Chapter 8, inspection and testing; 5.08(2) now reads only 'Delete sub-section 8.1.4.'
Why it exists
A sidewall vent terminal close to the ground can be buried by snowdrifts, covered by a deck or porch, or blocked by things stored against the house. When the exhaust can't get out, combustion products, including CO, can back up into the home. New England winters make snow blockage a predictable hazard, not a freak event. Massachusetts attacks it twice. The sign placed up high tells the homeowner the vent needs to be kept clear, and the required CO detector warns the family if it isn't.
How it came to be
- 2005 — Seven-year-old Nicole Garofalo of Plymouth dies of CO poisoning after snow blocks her home's heating vents. gloucester-ma.gov
- 2005 — Provincetown's account says it was January 2005 and the vent was blocked by snowdrifts. provincetown-ma.gov
- 2005 — Nicole's Law enacted: Acts of 2005, Chapter 123, approved November 4, 2005. malegislature.gov
- 2006 — HISTORY: the former 248 CMR 5.08(2) sidewall requirements were in print by February 2006, reproduced in a manufacturer's Massachusetts insert (Rev. 02/16/06). htproducts.com
- 2006 — HISTORY: the sign text under the former 5.08(2). The current 5.12(6) wording is 'GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS' (with a period). htproducts.com
- current — State Fire Marshal's winter advisory on blocked vents. capecod.com
- 2014 — 248 CMR 5.00 re-promulgated (Mass Register 1275, eff. 12/5/2014; 5.12 amended again eff. 4/30/2021). The sidewall sign becomes NFPA 54 12.9.7 via 248 CMR 5.12(6), and CO detection becomes 9.1.23 via 5.09(7). law.cornell.edu
Make it stick
Plymouth, January 2005: snow drifted over a family's heating vent, and a seven-year-old girl, Nicole Garofalo, died of carbon monoxide. Massachusetts named its CO alarm law after her.
On the exam
Expect the current MA rules. Sign: required when a through-the-wall vent is less than 7 ft above finished grade; mounted at least 8 ft above grade directly in line with the terminal; metal or plastic; letters at least 0.5 in.; exact text 'GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS' (248 CMR 5.12(6)). CO detector: battery or hard-wired, on the same floor as any vented gas appliance being installed or replaced; next adjacent floor for a crawl-space appliance; each habitable level in residences; detached uninhabitable garage exempt (5.09(7)). Also the 3 ft minimum from a gas meter for sidewall terminations and intakes, and snow-line rules (5.12(7)). Nicole's Law (MGL c.148 s.26F1/2, owner's duty to have CO alarms) and 248 CMR (installer's duty) are separate laws. The older 5.08(2) details (hard-wired with battery back-up only, 30-day grace period) are superseded; do not use them.
What people get wrong
- The sidewall rule was written because of Nicole Garofalo. UNVERIFIED. The timing is consistent: her death was in January 2005, and the former 5.08(2) was in print by February 2006. But no source was found linking the Board's rule to her case or giving its adoption date. Only Nicole's Law (Acts 2005 c.123) is verifiably named for her.
- The installer needs a hard-wired, battery-backup CO detector for every sidewall-vented appliance. That was the former 248 CMR 5.08(2). The current rule (5.09(7), NFPA 54 9.1.23 as replaced) accepts a battery-powered OR hard-wired CO detector, and it applies to installing or replacing ANY vented gas appliance, not only sidewall-vented ones. It must be on the appliance's floor (next adjacent floor for a crawl space) and, in residences, on each habitable level.
- The rule only matters for furnaces. The sign rule covers any through-the-wall vent less than 7 ft above grade (5.12(6)), and the CO detector rule covers every vented gas appliance installed or replaced (5.09(7)): furnaces, boilers, water heaters and others.
Try it: 3 real practice questions
Q1. In Massachusetts, a sidewall horizontally vented gas appliance in a dwelling has its vent terminal less than 7 ft above grade. The required sign reading GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS must be mounted in line with the terminal at a minimum height above grade of:
A low sidewall terminal can be buried by snow, decks or stored items, sending carbon monoxide back into the home. In Massachusetts, when a through-the-wall vent is installed less than 7 ft above finished grade, a metal or plastic identification plate must be permanently mounted at least 8 ft above grade, directly in line with the terminal. It must read GAS VENT DIRECTLY BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS in print at least 0.5 in. high, so it stays visible above snow. This is a Massachusetts amendment and is not in base NFPA 54.
248 CMR 5.12(6) (adds NFPA 54-2012 12.9.7 Signage)Q2. Through-the-wall vents for Category II and Category IV appliances shall not terminate:
Condensing appliances discharge a moist plume that drips acidic condensate and can form ice. Over a walkway that creates a slip hazard, and near regulators or relief valves it can freeze or corrode them. So terminating over public walkways, or where condensate or vapor could create a nuisance or hazard, is prohibited. Massachusetts (248 CMR 5.12(5)) deletes the last sentence of this subsection, but the walkway prohibition itself is unchanged.
NFPA 54-2012 12.9.4; 248 CMR 5.12(5)Q3. A mechanical draft venting system (not a direct-vent appliance) terminates through an exterior wall. Its terminal must be located at least:
A fan-driven exhaust plume rises as it leaves the terminal. A terminal below or beside an opening can therefore be drawn in, so it needs 4 ft of separation, while a terminal above the opening needs only 1 ft. The same clearances apply to gravity air inlets, and the bottom of the terminal must be at least 12 in. above grade.
NFPA 54-2012 12.9These come from the PressureTest bank. Start 7 days free for the full bank, timed exam simulations and drawn isometric problems.