LARGER VIEW of an octopus furnaceHeating System Safety Inspection Guide

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Here we explain safety procedures and tips that are important during heating system inspections.

This article series answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs.

We describe how to inspect, troubleshoot and repair heating and air conditioning systems to inform home owners, buyers, and home inspectors of common heating system defects. The articles at this website describe the basic components of a home heating system, how to find the rated heating capacity of an heating system by examining various data tags and components, how to recognize common heating system operating or safety defects, and how to save money on home heating costs. We continue to add to and update this text as new details are provided. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

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Heating Inspection Safety Guide

This section describes examples of steps to protect the home or heating system inspector during the inspection of a heating system. It does not address safety concerns for the client/occupant or unsafe conditions on the heating equipment itself, though those are addressed in other articles at this website. ASHI 9.3.A. The inspector is not required to operate equipment when weather conditions or other circumstances may cause equipment damage [or in the opinion of the inspector, may cause any sort of unsafe condition (added by DJF, NOT ASHI Standards)

In order to be as thorough, accurate, and safe as possible, a heating system inspector should use a well-defined order of discovery which assures that s/he examines all important heating system components. Several possible heating system inspection "road maps" can be used for this purpose and are described at this website.

  • Air Filter Shock Hazards: Avoid electric shock from the static charge at electronic air filters. - Home inspection standard example: ASHI 9.3.D.4 The inspector is not required to observe electronic air filter
  • Backpressure or Flashback: Watch for flashback or backpressure at inspection ports on heating equipment
  • Blocked heating flues: a blocked flue can cause the production of potentially fatal carbon monoxide gases in a building. A blocked flue case study is reported at UNLINED FLUE INSPECTIONS.
  • BLUE vs YELLOW COMBUSTION FLAMES - the Blueray history and blue flame vs. yellow flame combustion, flame color & combustion efficiency, & how oil competes with gas as a heating fuel.
  • Blueray Heating Boilers/Furnaces Safety Recall by the US CPSC, with additional history, photos, and technical details; Blue Flame Blue Ray
  • Carbon Dioxide Gas Toxicity
  • Carbon Monoxide Gas Toxicity, exposure limits, building inspection for CO hazards
  • Carbon Monoxide Poisoning Warning - Chimney Safety:US CPSC safety warning [Home Heating System Should Be Checked for proper venting and for CO Carbon Monoxide Hazards - clarifying notes by DJF]
  • CHIMNEYS & FLUES, ASBESTOS TRANSITE PIPE - chimney movement, chimney cracks, chimney safety inspection, chimney cleaning, draft problem diagnosis & repair
  • Chimney Inspection Checklist - detailed articles on a wide variety of chimney safety and functional defects
  • CHINESE DRYWALL HAZARDS - corrosion risks to HVAC condensing and cooling or heating coils, possible corrosion risks to HVAC metal ductwork from corrosive gases produced by Chinese drywall.
  • Combustion air: make certain that all fuel burning equipment has adequate combustion air. See COMBUSTION AIR for additional details about the requirement for combustion air. COMBUSTION AIR for TIGHT BUILDINGS explains how to provide outside combustion air for tight buildings. See COMBUSTION GASES & PARTICLE HAZARDS for an explanation of the dangers of inadequate combustion air. See COMBUSTION PRODUCTS & IAQ for the relationship between fuel burning appliances and building indoor air quality. More about carbon monoxide - CO - is at CARBON MONOXIDE - CO and at CARBON MONOXIDE WARNING.
  • Confirm Heat Operation Before Leaving: To avoid a future dispute about having been the cause of lost heat in a building, particularly in cold weather, if the system was on and running, observe and note that it was running normally at the end of the inspection procedure. This is important if your inspection procedure includes any action that may temporarily shut off the system such as testing a shutoff switch.
  • Corrosion on Heating Systems Do not pick at corrosion on heating systems - you may cause a catastrophic leak that requires immediate system shut-down - which in freezing weather risks freeze-damage to the building.
  • STAIN DIAGNOSIS on BUILDING INTERIORS, how to diagnose stains on walls, floors, carpets, and how to determine the stain source
  • Disassembling flue vent connections: Do not disassemble flue vent piping - risks of filth, unable to reassemble, etc.
    Home inspection standard example: ASHI 9.3.D.1 The inspector is not required to observe the interior of flues [However often you can detect a blocked flue by looking through the barometric damper or by use of a mirror at the chimney cleanout. We recommend this step. -DJF]
    Home inspection standard example: ASHI 9.3.D.2 The inspector is not required to observe fireplace insert flue connections [Normally not visible. Caution: there is frequently a hidden problem there.]
  • DUCT SYSTEMS - air leaks, unsafe ductwork, inadequate supply or return air, other defects
  • DUCT & AIR HANDLER ODORS - how to find and cure smelly duct work or air handlers
  • Ducts - Asbestos Transite Pipe
  • DUST, HVAC CONTAMINATION STUDY An Investigation of Indoor Dust Debris Blamed on a Heating/Cooling System Reveals Carpet Dust
  • FAN LIMIT SWITCH control on heating furnaces
  • NOISE / SOUND DIAGNOSIS & CURE includes a discussion of noises related to heating equipment
  • OIL BURNER NOISE SMOKE ODORS and also OIL BURNER SOOT & PUFFBACKS explain how to diagnose oil burner noises, smoke, odors, sooting, and which conditions are potentially dangerous, requiring prompt service or repair
  • Odors From Heating Systems - a list of articles addressing the sources of odors produced by various types of heating systems - how to find, diagnose, and correct these possibly dangerous conditions.
      BLUERAY Recall
      CHIMNEYS & Flues - Asbestos Transite
      Goodman HTPV RECALL
      Lennox Furnace Manuals
    US Consumer Product Safety Commission notices, contact information, claims
      Weil McLain RECALL
  • SOOT on OIL FIRED HEATING EQUIPMENT discusses sooty on or inside oil fired heating equipment and its effect on heating costs and heater operating problems. Also see OIL BURNER NOISE SMOKE ODORS.
  • STAIN DIAGNOSIS on BUILDING INTERIORS, how to diagnose stains on walls, floors, carpets, and how to determine the stain source
  • When to Shut Down Heating Systems: Turn off heating equipment immediately if you see conditions that appear to be unsafe, such as evidence of fire, smoke, puffback, or if you see safety controls such as relief valves, temperature limits, or flue gas spillage sensors which have been removed or modified, or if the equipment has already been "red-tagged" by a service technician.
  • When to Avoid Turning On Heating Systems: Do not turn on heating equipment if you see any condition that appears to be unsafe. Some examples are listed here.
    • Do not turn on equipment which has been "shut down" - Possible open piping, unsafe wiring, leaks, unsafe chimney, fire risks.
    • Do not turn on equipment which has been switched off without explicit permission/instruction from a responsible party
    • Examine gauges (not entirely reliable) for unusual pressure or temperature conditions and do not permit such equipment to continue to operate
    • Do not turn on, or turn off if already operating, any heating system whose temperature/pressure gauge shows abnormally high operating values
    • Do not operate equipment which does not appear to be vented properly; shut down equipment if, on operating it, you observe an apparently blocked flue
    • Do not operate equipment if the chimney is suspect--e.g. old single wythe unlined brick with visible damage in the attic or outside
    • Do not turn on, or turn off if already operating, any heating system that is not safely connected to a chimney
  • Humidifier Inspections: Be careful about disconnecting humidifiers to obtain access to furnace plenums: you may cut yourself on sheet metal, cause leaks in humidifier piping, cause spills.
    ASHI 9.3.D.3 The inspector is not required to observe humidifiers
    • But watch for humidifiers which leaked into and damaged duct work or onto and damaged a heat exchangers
  • Lighting test fires: Do not light fires in coal or wood stoves to check draft, etc
    Home inspection standard example: ASHI 9.3.C. The inspector is not required to ignite or extinguish solid fuel fires
  • Noises, smoke, soot, back pressure at inspection port (watch out for burns and fires if this port is opened), sloppy startup, rumbling, sloppy or delayed shutdown-flame lingers COULD indicate a very dangerous operating condition.
  • Relief Valve Testing on Heating Systems: Do not test relief valve levers nor catch your sleeve on one
    Home inspection standard example: ASHI 9.3.B. The inspector is not required to operate automatic safety controls
  • Shock Hazards at Heating Controls: Watch for electric shock at controls

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