Heat and Air Handbook pages are written to be accurate, useful, calm and fair to homeowners and technicians alike, and honest about where each fact comes from and what a page cannot know about your system. This page sets out how that works and where its limits are.
General information, not professional advice. Your system’s maker, your manual and a qualified technician decide what’s safe for your equipment, and local codes decide what needs a permit or a licensed installer. If you smell gas, leave the house now and call 911 or your gas utility from outside.
How a page is made
- Research. We start from the federal regulations in the eCFR and the Federal Register, EPA, DOE (live or in dated archive copies), ENERGY STAR, the safety agencies (CDC, CPSC, PHMSA, the US Fire Administration), EIA, and the makers’ own owner’s manuals, installation instructions and service documents, and note what they do and do not settle.
- Writing. A draft is written from that research under the Heat and Air Handbook name.
- Fact-check. A separate check compares each rule, date, minimum, code meaning, step, figure and document number with its source, and reworks every sum on the page.
- Graphics. Any diagrams or charts repeat facts from the text and add no new ones. Every rule in a graphic shows its source and the date it applies from. Our drawings show no brand names.
- Final review. A last read looks for errors, gaps, missing safety stops and anything that could mislead someone about their safety, their system or the law. If it finds a serious problem, the page is fixed and reviewed again. We do not publish a page with a serious problem still open.
Each page ends with the date its sources were checked. No process catches everything, so please tell us if you find a mistake.
Our sources
Every rule, date, minimum, figure, code meaning and safety step links to a primary source at the claim: the eCFR or the Federal Register, a federal agency’s own page, an archived copy of a federal page labelled with its capture date while the live page is down, a state statute or regulation in official text, or the maker’s own document on the maker’s site, named by number and edition. Model codes such as the International Residential Code are cited by section and edition as model codes, never as your local law. If we cannot confirm something, we leave it out or say plainly that it is not confirmed. Our how we check page explains how each kind of fact is handled.
HVAC contractor and service-company pages, parts sellers’ code lists and how-to pages, trade blogs, forums, videos, question-and-answer sites, home-improvement media and comparison sites are never a source, not for a rule, a figure, a code meaning or a step. Claims from sellers appear only as claims we have checked, without naming the seller. A maker’s document is a source for what that maker says about its own equipment, not a rule for every brand.
Rules for every page
A wrong step on a gas furnace or at an outdoor unit can hurt someone. So every page follows these rules:
- A clear note near the top. Every page says it is general information, not professional advice, that the maker, the manual and a qualified technician decide what’s safe for your equipment, and that local codes decide what needs a permit or a licensed installer.
- Gas and carbon monoxide first. Every furnace page, and every page that mentions the gas side, says what to do if you smell gas or a carbon monoxide alarm sounds before anything else, from PHMSA, CPSC, CDC and the makers. A furnace that has been under water is never relit.
- The owner line, stated. Problem pages say what you can check, where you stop, and what the technician will look at. Each step names the maker document it comes from. Where the maker reserves a job for a qualified technician or service agency, the page says so at that step, with the maker’s cautions.
- No refrigerant steps. Federal law (Section 608) requires certification for anyone who opens the refrigerant circuit, so pages give no steps to recharge, top up, recover or swap refrigerant, and suggest no substitute refrigerants.
- Owner electrical checks only. No page tells a reader to open an outdoor unit’s electrical panel, touch a capacitor or contactor, discharge anything or test with a meter, and no page tells anyone to bypass a safety switch or sensor.
- No national rule that doesn’t exist. Licensing, permits, carbon monoxide alarm rules in existing homes and who may do gas or electrical work are set by states and local governments. Pages say “codes are adopted locally; your building department decides”, and give a state’s rule only where read in its official text.
- Dated rules. Every federal minimum, refrigerant date and energy price carries the date it took effect or was read, and rules under legal review say so, with the day we checked.
- No personal verdicts. Pages explain the parts, the codes, the rules and the choices. They never say your system is safe, what is wrong with it, that a repair is within your skills, or whether to repair or replace it.
- Estimates, not decisions. Tools say “estimate”, show their working and never say “safe”, “up to code”, “legal” or “replace it”.
- No prices of ours. We publish no repair or replacement price tables. Where money matters, pages and tools use your own quote and EIA’s dated energy prices.
- No questions about your system, no referrals. We diagnose no one’s system, read no one’s codes for them, and name no contractor, technician, parts seller or maker as a recommendation. Where help matters, pages name the kinds of help: the maker’s own documents and support, a qualified technician, your gas utility and your building department.
What we do not claim
- We are not an HVAC contractor, an equipment maker, a parts seller or a utility.
- We do not claim to have serviced, repaired, installed or tested the equipment we describe.
- We do not invent authors, quotes, homeowner stories, repair results or reader comments.
- We do not rank or recommend furnaces, air conditioners, filters, thermostats, makers or contractors, and we do not call anything “best”.
- We give no lifespan figure for furnaces or air conditioners as fact, because we found no federal source for one.
- Photos are stock images chosen to illustrate a topic. They do not show homes or systems we know of. Some show a maker’s name on equipment; that is not a recommendation. We do not use images meant to frighten.
Fairness
Technicians are neither villains nor heroes, and a service call is a job with rules on both sides. Pages are written for anyone trying to understand a heating or cooling system: homeowners, renters, family members helping them, landlords, and people who work in the field. We say what the maker and the law ask of each side, including what federal law asks of technicians who handle refrigerant and what the efficiency rules ask of installers. Where sources disagree, as they do on filter intervals and filter ratings, we show each one and do not pick a winner. Sometimes the honest answer is that the maker’s document for your model, or a technician who has seen your system, has to answer the question.
Tools
Our tools are formulas and lookups with named inputs and shown working, and each formula is checked against answers worked by hand before it goes live. They use the rules and maker documents they name, with their dates, and the numbers you enter. Every default that is a rate or a rule says where it comes from, or that it is our assumption, and you can change it. Code lookups give the maker’s meaning in our own words and send you to the label inside your furnace door, which decides for your board. Results are estimates and information, never a diagnosis or a decision.
Updates and corrections
Federal rules, energy prices and makers’ documents change, so pages are rechecked on the schedule set out on our how we check page, and sooner when we learn a source they rely on has changed. A page shows an updated date only when its content really changed. Errors are fixed and recorded on our corrections page.
Advertising and independence
Display advertising pays for this site, and advertisers have no say over what we publish. We use no affiliate links, accept no paid placements, sell no leads, make no contractor referrals and publish no product rankings. Our about page has more on how the site works.