How long should an office be flushed before re-occupation?

WELL Building Standard A07 recommends a flush-out of 4500 m³/m² of outdoor air per square metre of floor area before occupancy. Where flush-out is impractical, BS EN ISO 16000-series air sampling for TVOCs and formaldehyde is the alternative compliance route.

What should a post-refurbishment air quality test cover?

TVOCs (BS EN ISO 16000-6), formaldehyde (16000-3 or -4), PM2.5 and PM10, CO₂ as a ventilation tracer, and temperature/RH. Sampling should run for at least 5 working days across the most heavily refurbished and most heavily occupied zones.

Guidance

Office Air Quality After Refurbishment

Refurbishment is the single most predictable trigger of an SBS complaint wave. Post-fit-out IAQ verification closes the gap between handover and healthy occupation.

Post-fit-out BS EN ISO 16000-series WELL A07 flush-out

Newly painted office furniture off-gassing VOCs

The pattern

Why refurbishment so often triggers an SBS wave

Refurbishment introduces large quantities of new material — paints, sealants, adhesives, MDF carcasses, laminate desktops, carpet tiles, acoustic panels — each contributing to a transient indoor VOC and formaldehyde load that can persist for weeks. At the same time, the building's ventilation paths are disturbed, supply diffusers are repositioned, and the BMS is recommissioned against an assumed (rather than actual) occupancy profile.

The result is predictable: occupants return, complaints follow within days, and the project team is left arbitrating between the fit-out contractor, the M&E contractor and the FM provider. Independent post-refurbishment IAQ testing breaks the deadlock with measured data.

Test scope

A post-fit-out IAQ test pack

Parameter	Method	Benchmark
TVOCs	BS EN ISO 16000-6 (Tenax / GC-MS)	WHO 2021 / WELL A05
Formaldehyde	BS EN ISO 16000-3 or -4	WHO 100 µg/m³ 30-min
PM2.5 / PM10	Optical particle counter	WHO 2021 AQG
CO₂	NDIR continuous logger	AD-F ≤ 1500 ppm
Temperature / RH	Calibrated probe	BS EN 16798-1 Cat II

FAQ

Post-refurbishment IAQ

New paints, adhesives, laminates, carpets and engineered timber off-gas formaldehyde and a wide mixture of VOCs for weeks to months after installation. Combined with disturbed dust, altered ventilation paths and BMS commissioning gaps, post-refurb periods produce a predictable spike in occupant complaints.

Refurb finished. Complaints rising.

Independent post-fit-out IAQ verification within days. Call 01322 555566.

Request post-refurb testing

Investigate

Talk to us