Ascomata 160-300 µm diam, ± spherical to ovoid, olivaceous to dark grey-green in reflected light, with well-developed brown rhizoids. Peridium brown, composed of textura intricata with hyphae 2-4 µm diam. Hairs covering the upper part of the ascoma, 3-5 µm diam at the base, rarely branched, flexuous, undulate or irregularly coiled, strongly verrucose. Interascal tissue none, at least at maturity. Asci 30-40 x 11-16 µm, clavate, long-stalked, evanescent at an early stage, 8-spored. Ascospores 9-12 x 8-10 x 6-8 µm, limoniform, with the ends weakly apiculate and one lateral face distinctly flattened, pale brown, relatively thick-walled, with one apical germ pore.
Colonies rapidly growing, with pale or olivaceous aerial mycelium and often with greenish or brownish exudates.
An extremely common and rather variable species; strains with coiled ascomatal hairs were historically identified as C. cochliodes and large-spored morphs as C. olivaceum. There are strains (sometimes considered as close relatives) that are heterothallic, often manifesting themselves in culture as immature ascomata with arrested development. As with other species of Chaetomium, mycotoxins such as chaetomin, chaetoglobosins and cochliodinol may be produced.
Isolated from soil, rotting vegetation, cellulosic products such as paper; also frequently encountered in surveys of fungi in indoor environments.
GB&I: England: Bedfordshire, Buckinghamshire, Cheshire, Derbyshire, Devon, Dorset, Essex, Hampshire, Herefordshire, Hertfordshire, Kent, Lancashire, Leicestershire, Lincolnshire, London, Norfolk, Northamptonshire, Oxfordshire, Staffordshire, Surrey, Sussex, Warwickshire and Yorkshire. Northern Ireland: Belfast, Fermanagh, Tyrone. Scotland: Lanarkshire, Midlothian, Perthshire, Shetland. Wales: Ceredigion, Glamorgan. Channel Is: unlocalized. Ireland: Carlow, Dublin, Galway. Otherwise cosmopolitan, frequently encountered in a wide range of habitats.