Silver in the air, measured

There is silver in the wax. The next fair question is what reaches the air while the candle burns.

That was measured in its own study, separate from any test of what the candle does in a room. It is reported here on its own too.

How it was measured

Two candles were burned for two hours each in a room-sized chamber. One had silver in the wax. The other was matched to it in every way except the silver, so any difference in the air would come from the silver alone.

The room was held at a steady temperature and humidity. A ceiling fan on low kept the air mixed, the way air moves in a lived-in room.

During the burn, a pump drew air from the room through a fine filter. Each filter was dissolved in acid and read by ICP-MS, short for inductively coupled plasma mass spectrometry. It is the standard instrument for finding trace metals, and it sorts atoms by their mass.

The study followed Good Laboratory Practice rules (21 CFR Part 58). Those are the federal rules for how a study is planned, recorded and archived, so that someone else can check the work afterward.

The number

Airborne silver during burn: max 1.01 ng/m³, ≥800× below NIOSH REL, ≥9,900× below OSHA PEL.

A nanogram is a billionth of a gram. The highest reading came from the last sample, taken at the end of the two-hour burn.

The limits it sits next to

Three US bodies publish limits for silver in the air people breathe.

OSHA permissible exposure limit. 10,000 ng/m³. OSHA is the federal agency that sets workplace safety law, and this is the legal limit for silver in American workplaces.

NIOSH recommended exposure limit. 900 ng/m³, its limit for the finest respirable silver particles. NIOSH is the federal research institute for workplace health. This is the strictest of the three, so it is the one the multiple is measured against first.

ACGIH threshold limit value. 100,000 ng/m³ for metallic silver. The ACGIH is the professional body of industrial hygienists, the people who measure air at work for a living.

All three are workplace limits, written as an average over a working day. They are the published benchmarks for breathing silver, and they are the benchmarks the study used.

The multiples in the line above are simple division: the limit, divided by the highest reading.

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Ordinary care still applies

These figures describe the air during a burn. They are not a substitute for ordinary candle safety.

Treat it as you would any lit candle: on a stable, level surface, away from drafts, children and pets, and never left unattended.

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Why silver is in the wax at all, and the two thousand years before it, is in Silver, in brief.

The full lab reports are on our science page.

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Sources

• Airborne silver during burn. Glow Guardian airborne silver study, ARE Labs. Linked from our science page.
• OSHA permissible exposure limit. Occupational Safety and Health Administration, Permissible Exposure Limits: Annotated Tables. https://www.osha.gov/annotated-pels
• NIOSH recommended exposure limits. National Institute for Occupational Safety and Health, NIOSH Pocket Guide to Chemical Hazards, DHHS (NIOSH) Publication No. 2005-149. https://www.cdc.gov/niosh/npg/
• NIOSH limit for the finest respirable particles. National Institute for Occupational Safety and Health, Current Intelligence Bulletin 70, DHHS (NIOSH) Publication No. 2021-112 (May 2021). https://www.cdc.gov/niosh/publications/numbered/2021-112.html
• ACGIH threshold limit value. American Conference of Governmental Industrial Hygienists, TLVs and BEIs (2023).