Hi, I'm the developer behind HeatSafe, a free heat safety app for outdoor and indoor workers.
I want to share why this app exists, and why — even though I started in South Korea — a growing number of US safety managers are finding it useful too.
It started with a simple gap
I wasn't a safety consultant or a construction manager. I was a developer who noticed something small but annoying: there was no simple, mobile-first tool to calculate heat stress risk on the spot. Weather apps show you the forecast for a city. They don't show you what it actually feels like standing on asphalt next to a running excavator.
So I built a simple calculator first — nothing fancy, just temperature and humidity in, risk level out.
Then I found out what safety managers actually needed
After release, I started looking into safety communities to understand who was using it and why. What I learned was that a number wasn't enough. Managers needed a way to show, after the fact, that they had actually checked conditions and taken action — not just remembered to.
That's the gap HeatSafe tries to close: measurement, evidence (photos), rest timers, and a one-tap PDF report, instead of a notebook and a spreadsheet at the end of the day.
Why this matters for US teams right now
The US doesn't yet have a finalized federal heat standard — OSHA's proposed rule is still in the rulemaking process. But that doesn't mean there's no exposure. OSHA's National Emphasis Program on heat hazards (CPL 03-00-024) was renewed in April 2026 and runs through 2031, and enforcement under the General Duty Clause is active today. On top of that, states like California, Oregon, and Washington already have their own binding heat rules.
In practice, that means many US employers are being asked the same question Korean and Japanese employers already face: "Can you prove you actually checked conditions and responded?" A written plan helps. A dated, timestamped record helps more.
What HeatSafe does
- Real-time Heat Index / WBGT: Pulls local temperature and humidity automatically, or lets you enter site-measured values directly.
- Photo evidence: Attach up to 3 photos per log entry — thermometer readings, shade structures, water stations — timestamped and geotagged.
- Smart rest timers: Set automatically based on your current risk level.
- One-tap PDF reports: Turn a day's worth of logs into a clean report you can hand to an inspector or a supervisor.
An honest note on limits
HeatSafe is a personal project, not a certified compliance product. It references public standards (NIOSH, OSHA guidance, ISO 7243) but it doesn't replace a Heat Illness Prevention Plan or legal advice specific to your state. Think of it as the tool that makes doing the right thing easier — not the thing that makes doing it optional.
It's free to use, with a small banner ad to help cover running costs. If that ever changes, I'll say so here first.
If your team is still tracking heat conditions on paper, I'd genuinely like to know if this helps.