Codes & Standards
Federal HVAC rules, efficiency standards, permits, tax credits and rebates, with effective dates and citations checked against the eCFR and Federal Register.
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Mercury Thermostat: How to Spot One, State Disposal Laws and Where to Recycle It
How to tell if a thermostat has mercury, what federal universal waste rules and seven verified state laws require, where to recycle one for free, and what EPA…
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Chimney Liner Rules: When Code Requires One, Which Type and How It Is Sized
When code requires a chimney liner, which type fits wood, oil, Category I gas and condensing appliances, how liners are sized, and why an orphaned water heater forces…
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Combustion Air: The IRC and IFGC Rules, Opening Sizes and a Worked Example
Combustion air rules from IRC G2407 and IFGC 304, quoted section by section: the 50 cubic foot method, the infiltration equations, every opening size, and a furnace plus…
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Negative Pressure Room: CDC and ASHRAE 170 Rules for ACH, Pressure and Exhaust
How a negative pressure room works and what CDC and ASHRAE 170 require: air changes, the 0.01 in. w.g. differential, exhaust discharge, monitoring and temporary HEPA conversions.
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Local Law 97: NYC Building Emissions Limits, Penalties and a Worked Example
Local Law 97 caps emissions from New York City buildings over 25,000 sq ft. We quote the limits and coefficients from the rule, show year-one results, and work…
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Ventless Gas Heater Safety: Code Limits, State Bans and the Moisture Math
We read the IRC and IFGC sections, state statutes, CPSC death estimates and a 30-home field study, then computed how much water and CO2 a ventless gas heater…
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Fume Hood: Face Velocity, ASHRAE 110 Tests, Hood Types and Energy Use
How a lab fume hood works, why OSHA no longer prints a face velocity, what Z9.5 and Cal/OSHA require, how ASHRAE 110 AM, AI and AU tests work,…
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Gas Bans by State in 2026: Which Laws Are Live, Paused, Preempted or Struck Down
A verified status table of US gas bans and the state laws that block them, read in statute and court text: New York, NYC, Berkeley, California air districts,…
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Landlord Air Conditioning Laws by State and City: Maximum Indoor Temperatures
Cooling rules for rentals in nine jurisdictions, read from the code text: who is covered, the maximum indoor temperature, the season, and what tenants can do when the…
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Landlord Heat Requirements by City and State: Minimum Temperatures and Dates
Minimum heat rules for rentals in nine jurisdictions, read from the code text: heat season dates, day and night minimums, how temperature is measured, and where tenants file…