The importance of humidification
Gas-fired humidifiers such as the Neptronic SKG can put 100 kg/h of moisture into the air. They are also said to be 75% cheaper to run than electrode boiler steam humidifiers, resulting in a payback of about 12 months when replacing an existing electrode boiler units.
RIK PROWEN examines the effects of indoor dry air, its causes and how to eradicate the problem.Headaches, sore throats, sore eyes, skin irritation and contact-lens discomfort are all symptoms of a dry indoor environment. Unfortunately we are not well equipped to notice a dry atmosphere in the same way as we notice being unusually cold or warm. We therefore commonly fail to associate discomfort or health problems with low relative humidity. The ideal indoor relative humidity (RH) is 40 to 60%, a figure endorsed by HEVAC, CIBSE, BSRIA and BRE. The Health & Safety Executive in its ‘Display screen equipment regulations 1992’ obliges employers to maintain a humidity that prevents discomfort and problems of sore eyes where people work at computer terminals for long periods. However, offices throughout the UK are often well below this level. A study by Volvic into 500 workplaces found that one in five offices in the UK were as dry as the Sahara desert, with 25% RH, and 10% as dry as California’s Death Valley, with only 23% relative humidity. Effects of low RH
One of the first noticeable effects of dry air is electrostatic shocks, which occur below 40% RH and can rapidly become a nuisance. Above this RH electrostatic shocks are eliminated. Eyes are particularly susceptible to dry air as the thin layer of moisture on the cornea quickly evaporates. Contact-lens wearers express discomfort that can increase fivefold as RH drops from 45% to 20%, by which stage dust and dirt deposits on lenses increase and cause greater irritation. If the air is too dry the skin, scalp and hair also begin to suffer. With no exposure to moisture, skin develops rashes and rough patches, the scalp starts to flake and hair will become brittle. The nose and throat act as a powerful humidifier for inhaled air, and mucous protects against infection by trapping microbes and dust. They start to dry up below 55% RH, quickly resulting in nasal stuffiness, dry mouth and sore throat. Persistently low RH increases susceptibility to infections such as colds and coughs. People’s perception of warmth varies with RH, and it is possible to maintain a sensation of warmth with reduced ambient temperature when humidity is at a comfortable level, so reducing heating costs. Causes
In the UK, low RH in the workplace occurs primarily in winter when heating is on. A typical office without humidification will experiences RH below 40% for about a third of the year. Further north, the problem is more extensive. Exceed the design specification of the building with more people, additional computer equipment and office machines, and the problem worsens as the indoor temperature rises. A third of the year is a significant proportion and should not be ignored, as employee welfare is an important issue. Commercially it makes sense, too; comfortable people are more productive. Solution
To ensure a comfortable, healthy and productive office environment of at least 40% RH, it is essential for most offices to employ some method of humidification. Incorporating a well-designed humidifier within a building’s air-conditioning system will eliminate dry-air problems. All too often the humidifier is the last thing to be considered when planning building services, even to the point of omitting it altogether where cost is an issue and simply leaving a space for a steam humidifier to be fitted later. However, as the cost of retrofitting humidification has been estimated at five times more than incorporating the equipment originally and, combined with the cost of running and maintaining a steam humidifier compared with the alternatives, simply leaving a space for a steam humidifier if building occupants demand it is not best practice. There is a variety of factors to consider in selecting the right humidifier for a building — including energy use, Legionnaires’ Disease legislation, water supply, cold water or steam, gas or electric, evaporative or spray, humidifier situation, control compatibility and maintenance needs. It is therefore important to work with a specialist who can provide guidance on the right type of humidifier for your use. It is also important to work with a company that can provide a full range of services, including installation and after-sales service and spares. As humidifiers handle water, they need to be looked after. Particularly important is the capacity for a supplier to offer a fully qualified commissioning service. With respect to legionellosis, for example, the HSE endorses the idea that the best people to commission equipment are the manufacturer or supplier. A planned maintenance schedule should be implemented thereafter to ensure the initial investment is not wasted. Several members of HEVAC’s humidity group can provide the required range of products and services.* Members also adhere to codes of best practice in delivering services to clients, and work to further good practice in humidification. Membership can therefore be a useful guide to choosing a prospective supplier. Rik Prowen is operations director with JS Humdifiers, Rustington Trading Estate, Artex Avenue, Rustington, West Sussex BN16 3LN.