Use of Formaldehyde for the Disinfection of Hospital Woollen Blankets in Laundering

Abstract

The value of formaldehyde in the penultimate or last laundering rinse is assessed, using a micrococcus and Eschem'chia coZi as the indicator organisms. Experiments demonstrating a residual disinfecting effect of dry formaldehyde treated blankets against the micrococcus are also described. PREVIOUS WORK (Dickinson, Wagg & Carter, 1962) showed the effectiveness of a long presoak in a 0.5% (w/v) solution of formaldehyde as a means of disinfecting woollen blankets in laundering. This process was too long for routine use and so a much shorter method was developed in which formaldehyde was put in the last rinse lasting for only 14 min.Alder (pers. comm.) showed that blankets treated with steam and formaldehyde in an autoclave at 90" under subatmospheric pressure may show residual disinfectant action in the dry condition. Moreover, Kingston & Noble (1964) have demonstrated the self disinfecting properties of various dry surfaces which slowly evolve formaldehyde. This suggested that the formaldehyde left on the blankets from the new laundering technique might similarly make them self disinfecting, and, indeed, results indicated this, a t least, a t 44% relative humidity (RH). The smell from blankets treated with formaldehyde in the last rinse was objectionable, particularly when the blankets were stored in a confined space, and to avoid this a modified technique with formaldehyde in the penultimate rinse was investigated.Although the residual effect against dry bacteria was less than it was when the formaldehyde was in the last rinse, it was still considerable. It seems likely that the modified technique will prove to be a reasonable compromise, as the smell of formaldehyde was greatly reduced. It is important to note that Alder (pers. comm.) found that the initial smell from his formaldehyde autoclaved blankets disappeared and yet still there was a residual bactericidal effect on stored blankets. Experimental Disinfection in launderingThe Standard Washing Process described previously (Dickinson et al., 1962) was used as a typical laundering procedure. The disinfection process consisted simply of adding the formaldehyde to the penultimate or ultimate rinse extended t o 14 min. After this, the blankets were hydro extracted and tumbler dried.

Types of Antimicrobial Agents

“…Formaldehyde vapour has found use as a disinfectant in the following situations (Russell, 1976): 1 in combination with low-temperature steam (70-90 °C) as a method for disinfecting heatsensitive materials (Alder et al, 1971(Alder et al, , 1990). This will be discussed later (Chapter 12.1); however, some studies (Wright et al, 1996) have cast doubt on the efficacy of this process as a sterilization method because it has been possible by means of a post-heating shock to revive some treated spores; 2 rarely, in the disinfection of hospital bedding and blankets, when formaldehyde solutions are used in the penultimate rinse of laundering blankets to give a residual bactericidal activity because of the slow evolution of formaldehyde vapour (Dickinson & Wagg, 1967;Alder et al, 1971Alder et al, , 1990; 3 in the terminal disinfection of premises, although this is considered to be of limited value (Kelsey, 1967); 4 as a fumigant in poultry houses after emptying and before new stock is introduced (Nicholls et al, 1967;Anon., 1970) and in the hatchery to prevent bacterial contamination of shell eggs (Harry, 1963); 5 in the disinfection of safety cabinets.…”