This review examines whether there is a direct or indirect relation between damp or mould in the home and respiratory health. Home dampness is thought to have health consequences because it has the potential to increase the proliferation of house‐dust mites and moulds, both of which are allergenic. The results from the many studies conducted to investigate whether damp and mould are associated with health outcomes are diffecult to compare because the methods of measuring exposures and helth outcomes have not been standardized. However, the studies that have been conducted in children are probably the most reliable because the confounding effects of active smoking or occupational exposures are absent, and because the presence of symptoms of cough and wheeze have been consistently investigated in many studies. The increased risk of children having these symptoms if the home has damp or mould is fairly small with an odds ratio that is generally in the range 1.5–3.5, these estimates being statistically significant when the sample size has been large enough. This range is consistent with the measured effects of other environmental exposures which are considered important to helth, such as environmental tobacco smoke or outdoor air pollutants. The potential benefits or reducing mould in the home have not been investigated, and the few studies that have investigated health improvement as a result of increasing ventilation or reducing damp in order to reduce house‐dust mite levels suggest that this intervention is expensive, requires a large commitment, and is unlikely to be successful in the long term. This implies that houses need to be specifically designed for primary prevention of respiratory problems associated with indoor allergen proliferation rather than using post hoc procedures to improve indoor climate and reduce allergen load as a secondary or tertiary preventive strategy.

A highly efficient Ho 3+ -doped fluoride glass fibre laser operating at 2.08 mm is demonstrated using diode pumping at a 1.94 mm wavelength. A maximum slope efficiency of 78% and output power of 516 mW has been obtained.Introduction: Fibre lasers that emit light at 2.1 mm have attracted much interest recently because of the large number of potential applications that involve the atmospheric transmission window between 2.1 and 2.25 mm. Fibre lasers exploiting the 5 I 7 5 I 8 transition of Ho 3+ offer the most efficient route to high power emission in the 2.1 to 2.2 mm region. To date, the highest power from Ho 3+ -based fibre lasers has been generated using Tm 3+ co-doping and diode pumping at 790 nm [1]; however, the largest slope efficiency has involved pumping the upper laser level directly using high power Tm 3+ -doped silicate glass fibre lasers [2,3]. Diode pumping of singly Ho 3+ -doped fibre lasers at 1150 nm [4] provides a simple laser arrangement and potentially better energy storage; however, the highest slope efficiencies for pumping at this wavelength are approximately 51%.Recent developments in research into high power diode lasers emitting radiation at 1.95 mm [5] have opened up the opportunity to diode pump Ho 3+ -based glass fibre lasers directly into the upper laser level and at the peak of the 5 I 7 absorption in a similar way to Ho:YAG lasers [6]. In addition, the resultant large Stokes limit of 93% allows the use of fibre materials that have weaker thermomechanical properties but lower phonon energies compared to silicate glasses. In this Letter, we report the use of direct diode pumping of a Ho 3+ -doped fluoride (ZBLAN) fibre laser operating at 2.08 mm with diodes emitting at 1.94 mm. A slope efficiency of 78% with respect to the absorbed pump power was obtained which we believe may be limited by pump light absorption in the polymeric second cladding of the Ho 3+ -doped fluoride double-clad fibre.

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