Safe Formaldehyde Levels & How Testing Works

The WHO indoor air guideline for formaldehyde is 0.1 mg/m³, measured as a 30-minute average — the same figure Singapore's SS 554:2016 code of practice uses for air-conditioned buildings. SS 554 itself covers offices and other non-residential premises rather than homes, but it is the local benchmark homes are usually measured against. Readings below about 0.06 mg/m³ are comfortably safe, readings between 0.06 and 0.1 are within the guideline, and readings meaningfully above 0.1 warrant action. Formaldehyde is classified as a Group 1 carcinogen by the IARC, which is why the guideline exists — but the number on a calibrated meter, not the smell, is what tells you where your home stands.

What the numbers mean

Most professional meters display milligrams per cubic metre (mg/m³); some also show parts per million (ppm). The conversion is roughly 1 ppm ≈ 1.23 mg/m³ at 25°C, so the WHO guideline of 0.1 mg/m³ is about 0.08 ppm. In practical bands:

Reading (mg/m³)	Same reading (ppm)	Band	What it means
Below 0.06 mg/m³	Under 0.05 ppm	Safe	Typical of established homes. No action needed.
0.06–0.10 mg/m³	0.05–0.08 ppm	Acceptable	Within the guideline. Worth re-checking if a renovation is recent.
0.10–0.30 mg/m³	0.08–0.24 ppm	Elevated	Above the guideline; eye, nose and throat irritation is possible with prolonged exposure. Treat, or ventilate aggressively and re-test.
Above 0.30 mg/m³	Over 0.24 ppm	Significantly elevated	Avoid prolonged occupancy until levels are brought down and verified.

A just-renovated bedroom with new built-in wardrobes commonly reads in the elevated band — something like 0.24mg/m³ — while the post-treatment target for every room is 0.06mg/m³ or lower.

Got a number from a home meter? Check it first

Most readings people worry about come from S$20–80 handheld meters. Their semiconductor sensors cross-react with alcohol, cooking fumes, perfume and humidity, so a single high number is a prompt to verify, not a verdict. Before trusting it: close windows and doors for 8–12 hours, measure at breathing height away from the kitchen and fresh perfume, check the unit (0.08 ppm is about 0.10 mg/m³, not 0.08), and watch the trend over several days.

If it keeps reading above 0.1 mg/m³ (0.08 ppm), confirm it with a calibrated electrochemical meter. In Singapore, Formaldehyde.SG tests every room at breathing height, plus inside wardrobes and cabinets, for S$100, with a written report benchmarked against the WHO guideline — and the fee is waived if you go ahead with removal. See how formaldehyde testing works, or which home meters can be trusted.

Why smell is an unreliable gauge

Two things make your nose a poor instrument here. First, olfactory fatigue: spend time in a home with elevated formaldehyde and you stop noticing the smell within hours, while the level itself hasn't changed. This is why owners often report that the smell "went away" after a week of living in — and why visitors notice it immediately.

Second, the detection threshold varies widely from person to person, and for many people it sits near or above the guideline itself. You can have a home reading above 0.1 mg/m³ that smells like nothing to you, and a safe home that still carries a faint new-furniture odour from other, harmless compounds. The smell and the number are loosely related at best — which is the whole case for measuring. (For what that renovation smell actually is, see what off-gasses and for how long.)

How professional testing works

A meaningful test reflects the conditions you actually live in. Formaldehyde.SG asks clients to keep windows and doors closed for 8–12 hours beforehand — overnight is ideal — so readings show what the home equilibrates to with the aircon running, not what it reads after a morning of airing out. On the visit, each room is measured at breathing height, plus inside wardrobes and cabinets, where emissions concentrate. Professional services use calibrated electrochemical meters, which respond specifically to formaldehyde and are checked against reference standards.

The consumer handhelds sold online for S$20–80 use semiconductor sensors that cross-react with alcohol, cooking fumes, perfume and humidity — they can read several times too high or too low depending on what else is in the air. They're fine for watching a trend in one room over weeks; they are not something to base a move-in decision on.

What to do at each band

Safe (below 0.06): nothing. Genuinely. Keep the report for your records — useful if you later add furniture or renovate.
Acceptable (0.06–0.10): no action required. If the renovation is recent or a baby is on the way, re-test after a few weeks, since levels move with heat and humidity.
Elevated (0.10–0.30): either ventilate aggressively for several weeks and re-test, or book formaldehyde treatment for a verified result — the sensible default if you're moving in soon.
Significantly elevated (above 0.30): hold off on moving in, treat, and re-verify before occupancy — particularly with infants, pregnancy or respiratory conditions in the household.

If you don't yet have numbers, Formaldehyde.SG's S$100 testing visit gives you the room-by-room readings this guide is written around — and sometimes the news that you don't need anything else.

Common questions about formaldehyde readings

What is the safe level of formaldehyde in Singapore?

The benchmark is the WHO indoor air guideline of 0.1 mg/m³ (about 0.08 ppm), averaged over 30 minutes. Singapore’s SS 554:2016 code of practice uses the same 0.1 mg/m³ figure for air-conditioned buildings; SS 554 covers offices and other non-residential premises rather than homes, but it is the local benchmark homes are usually measured against. Readings below about 0.06 mg/m³ are comfortably safe.

Is a formaldehyde reading of 0.08 safe?

It depends on the unit. 0.08 mg/m³ is within the WHO guideline of 0.1 mg/m³ — acceptable, though worth re-checking after a recent renovation. 0.08 ppm is about 0.10 mg/m³, right at the guideline limit, so it is worth confirming with a calibrated meter and bringing down, especially in bedrooms and nurseries.

Is 0.1 mg/m³ of formaldehyde safe?

0.1 mg/m³ is the guideline limit itself, not a comfortable target. It is set to prevent sensory irritation in most people. A home that reads at or just above it with the aircon running is worth ventilating and re-testing, and a bedroom or nursery is worth bringing below 0.06 mg/m³.

Is 0.2 ppm formaldehyde dangerous?

0.2 ppm is about 0.25 mg/m³ — roughly two and a half times the WHO guideline. It is not an emergency, but sensitive people such as children and asthmatics often report eye, nose and throat irritation at that level, so it is worth acting on: confirm the reading first if it came from a handheld meter, then treat the source or ventilate aggressively and re-test.

How accurate are cheap formaldehyde meters?

Not accurate enough for a move-in decision. Consumer handheld meters, typically S$20–80, use semiconductor sensors that cross-react with alcohol, cooking fumes, perfume and humidity, and side-by-side comparisons often show them reading several times too high or too low. They are useful for watching a trend in one room; confirm any high reading with a calibrated electrochemical meter.

Safe formaldehyde levels & how testing works