Legal

Disclaimers

Read together with the Terms of use. Short version: we explain the science honestly, but you act at your own risk, and emergencies belong to professionals.

Not medical advice — no doctor-patient relationship

ppmail.me describes environmental factors that can contribute to common symptoms. It does not diagnose, treat, or prevent any condition, and reading it creates no clinician-patient relationship. Symptoms discussed here (headache, fatigue, cognitive complaints, poor sleep) have many causes, some serious. Persistent, severe, or worsening symptoms belong with a qualified clinician — promptly, and regardless of what any air measurement shows. Never delay or abandon professional care because of something read here. In a medical emergency, call your local emergency number (911 in the US).

Emergencies are not a reading assignment. Suspected carbon monoxide (a different gas from CO₂ — colorless, odorless, lethal), a gas smell, a wildfire evacuation order, difficulty breathing: leave, get fresh air, and call emergency services. A CO alarm is a $25 non-optional device wherever anything burns fuel. No web page — including this one — is the right tool for an emergency.

Estimates, calculators & the limits of numbers

Room-air figures on this site (e.g., "a small meeting room gains ~1,000 ppm an hour") are order-of-magnitude estimates from published generation rates, labeled as such where they appear; your room, car, or classroom will differ. The CADR calculator produces sizing guidance, not a safety specification, and assumes typical rooms and honest manufacturer ratings. Consumer CO₂ monitors have real error bars and drift. None of these numbers is a substitute for professional assessment of ventilation, combustion safety, or occupational exposure — and workplace air is additionally governed by law and by your employer's obligations, not by this site.

The science can move

We cite peer-reviewed sources accurately as of each page's review date, we verify DOIs, and we present contested findings as contested (see the caveat boxes). Studies can be revised, disputed, or retracted; standards bodies update their numbers. Where our text and a current official standard disagree, follow the standard.

Products, DIY & safety

Product mentions are unpaid editorial examples, not endorsements; we have no relationship with any manufacturer, and product performance claims are the manufacturer's. Use all devices per their instructions. DIY builds described here (such as the box-fan filter) are undertaken at your own risk: use a modern UL-listed fan, assemble and operate per the published public-health guidance we cite, and don't leave improvised equipment running unattended if its maker says not to. Never use ozone-generating devices in occupied spaces.

Advertising & affiliate status

Pages may display ads (Google AdSense); advertisers' claims are their own, and an ad's appearance is not our endorsement. As of August 30, 2026 the site contains no affiliate links and has received no payment, product, or consideration from any company mentioned. If affiliate links are ever added, the pages carrying them will say so plainly and this page will be updated.

External links

Linked third-party sites (including government and academic resources) are outside our control; links are provided for reference and may break or change.

No guaranteed outcomes

Ventilation, filtration, and measurement are well-supported general practices — but we do not and cannot promise they will resolve any particular symptom, achieve any particular reading, or produce any particular result in your specific circumstances.