If your workforce breathes living particles, you need to know what's in the air.

Why bio-aerosols matter under COSHH

Biological agents — bacteria, fungi, viruses and the cell-wall fragments they shed (endotoxin, β-glucans, mycotoxins) — are explicitly classified as hazardous substances under Schedule 3 of COSHH 2002. Inhalation can drive occupational asthma, hypersensitivity pneumonitis (extrinsic allergic alveolitis), ODTS, chronic bronchitis and, for opportunistic pathogens such as Aspergillus fumigatus, invasive infection in immunocompromised wearers.

Unlike chemical exposures, there is no single Workplace Exposure Limit for most bio-aerosols. Instead, regulators publish position statements and sector benchmarks: the HSE composting position (1,000 CFU/m³ A. fumigatus at the receptor), the DEFRA M9 monitoring framework, AfPP and HSE guidance for metalworking-fluid mist (1 mg/m³ inhalable, with bacterial counts <10⁶ CFU/ml in the sump), and the Dutch DECOS health-based recommended OEL for endotoxin of 90 EU/m³.

Sampling methods we deploy

Culturable bacteria and fungi are sampled with Andersen single-stage impactors onto tryptone soya agar (bacteria, 30 °C, 48 h) and malt extract agar (fungi, 25 °C, 5–7 d), with selective Sabouraud / DG18 plates for Aspergillus speciation. Endotoxin is sampled onto polycarbonate filters and analysed by kinetic chromogenic LAL assay reported in EU/m³.

For metalworking-fluid mist, we run inhalable IOM heads in parallel with sump-sample collection — quantifying both the airborne mist concentration (mg/m³) and the in-sump bioburden (CFU/ml of bacteria, plus mycobacteria screening where the application risk warrants).

Where speciation matters — for example confirming or excluding Legionella pneumophila, Mycobacterium immunogenum or specific moulds — we add culture-based microbiological speciation through a UKAS-accredited microbiology lab.

Composting, AD and waste sites

The HSE M9 framework and the Environment Agency permitting position both require bio-aerosol monitoring at composting, in-vessel composting and open-windrow sites where sensitive receptors lie within 250 m. Sysco delivers the standard suite — total bacteria, total fungi, gram-negative bacteria, A. fumigatus and endotoxin — at source, downwind and at the receptor in a single visit, with full meteorological logging.

Reports are formatted to satisfy permit conditions and the EA's review process, with statistical comparison to background and an interpretation against the 1,000 CFU/m³ A. fumigatus benchmark.

Metalworking-fluid mist and sump bioburden

Water-mix metalworking fluids support bacterial and mycobacterial growth that drives occupational asthma and hypersensitivity pneumonitis — the HSE has issued multiple safety alerts after UK outbreaks. We measure inhalable MWF mist in the breathing zone (target <1 mg/m³), sump bioburden (target <10⁶ CFU/ml total bacteria), and screen for non-tuberculous mycobacteria where the application or symptom history justifies it.

Findings are tied back to fluid-management practice: concentration, pH, tramp-oil contamination, top-up regime and biocide dosing — so the result is a usable corrective programme, not just a number.

How a microbiological survey runs

We attend with calibrated Andersen impactors, IOM heads, BioSamplers and sterile media prepared the same morning. Sampling runs are typically 5–15 minutes per impactor location to avoid plate overload, with parallel 4-hour filter runs for endotoxin. Samples are couriered same-day to the UKAS-accredited microbiology lab; culturable results take 48 h (bacteria) to 7 days (fungi), endotoxin and microbiological speciation 5–7 working days.

The report sets each result against the relevant benchmark (HSE, DEFRA, AfPP, DECOS), apportions sources, and recommends process, ventilation or fluid-management controls. A non-technical executive summary sits on top for permit, board or HSE submission.