Humidity shifts particle size, stickiness and how easily dust re-enters the air. Understanding the physics helps you choose controls that work every day, not just on dry or damp days.

What high humidity does

• Hygroscopic growth: many particles absorb water and swell. Larger particles settle faster, but the moisture film makes them adhere to surfaces and clog filters and ducts.
• Agglomeration: particles clump together, changing how they travel and deposit. Build-up on ledges and cable trays increases, making housekeeping slower.

What low humidity does

• More re-suspension: drier, lighter particles are easily kicked up by footfall and air movement, increasing the PM1/PM2.5 fraction that stays airborne.
• Static effects: very low RH can increase electrostatic attraction and nuisance shocks, complicating handling and cleaning.

Practical implications for control

• Stabilise RH: aim for a steady mid-range (about 40–55% RH) to avoid sticky build-up on damp days and excessive re-suspension on dry days. Dehumidifiers can help hold this band where moisture loads are high.
• Tune capture: on humid days, check pre-filters and ducts for caking; on dry days, prioritise capture at source and avoid sweeping that re-launches fines.
• Air cleaning and housekeeping: keep H-Class vacuums and H13/H14 filtration in service; adjust cleaning frequency with the season rather than using a fixed schedule.
• Monitor trends: a simple RH reading beside a PM monitor explains why counts change and guides the right response.

By planning for humidity swings, controls stay effective year-round and staff have clear reasons for adjusting tasks, from filter checks to when to run dehumidifiers.