Aerosol production efficiency

Ultrasonic nebulization has two advantages over pneumatic nebulization. The aerosol particles have a lower diameter and a narrower particle size distribution compared with pneumatic nebulization (< 5 compared with 10-25 pm). Therefore, aerosol production efficiency may be up to 30%, and analyte introduction efficiency is high. No gas flow is required for aerosol production, the trans-... 

Once experimental conditions have been fixed, the aerosol production efficiency also depends on physical parameters related to the liquid nature. It has been shown (Gershenzon, 1964) that, at constant ultrasonic power level, the production yield is an increasing function of the ratio r. 

Aerosol products are hermetically sealed, ensuring that the contents caimot leak, spill, or be contaminated. The packages can be considered to be tamper-proof. They deUver the product in an efficient manner generating Httie waste, often to sites of difficult access. By control of particle size, spray pattern, and volume deUvered per second, the product can be appHed directiy without contact by the user. For example, use of aerosol pesticides can minimize user exposure and aerosol first-aid products can soothe without applying painful pressure to a wound. Spray contact lens solutions can be appHed directiy and aerosol lubricants (qv) can be used on machinery in operation. Some preparations, such as stable foams, can only be packaged as aerosols. 

As in the case of the BDP solution aerosol, enhanced efficiency of aerosolization, leading to high lung deposition compared with an equivalent suspension product. 

The other method of classifying an aerosol product is by determining the chemical heat of combustion of all of the constituents within the aerosol can. This method provides consistent correlation with the 12-pallet aerosol classification test. The chemical heat of combustion is the product of the theoretical heat of combustion and combustion efficiency. An aerosol product is considered Level 1 if the chemical heat of combustion is greater than 0 and less than or equal to 8600 Btu/lb (20 KJ/g), Level 2 if it is greater than 8600 Btu/lb (20 KJ/g) and less than or equal to 13,000 Btu/lb (30 KJ/g), and Level 3 if it is greater than 13,000 Btu/lb (30 KJ/g). NFPA 30B requires that the classification of an aerosol product be stated on the carton to allow easy identification. 

A listing of the theoretical heats of combustion, combustion efficiencies and chemical heats of combustion for a number of chemicals commonly found in aerosol products is shown in Table 2-7. 

Ultrasonic nebulizers are free of these difficulties as aerosol production is independent of gas flow, and droplet size is related to ultrasonic frequency. Droplets with diameters of 1 pm can be obtained with frequencies above 1 MHz. The efficiency is high enough to require the addition of a desolvation system to eliminate water. The desolvation system consists of an oven associated with a cooling system to trap the water vapor. Detection limits are usually improved by a factor of 10 in comparison to a pneumatic nebulizer. Although ultrasonic nebulizers are attractive in this respect, their use is as yet not widespread, due to their prohibitive cost. 

BS EN 1822-2 2010, High efficiency air filters (EPA, HEPA, and ULPA). Aerosol production, measuring equipment, particle-counting statistics... 

The tremendous effort of I.V. Petryanov-Sokolov and collaborators led to first industrial facility for electrospinning fibrous material in the late 1930s for gas masks. The electrospun fibres were named after Petryanov as Petiyanov fibres (PF) and showed excellent filtration properties such as high breathability, aerosol capturing efficiency and long shelf life. But due to security reasons and military secrets the products were confined to USSR [16]. The first commercial sub-micron nanofibre products were introduced to market in USA by Donaldson co., in 1980s [17], by Dupont in 1995 [17, 18] and Reneker and co-workers in 1995 [17, 19, 20]. 

The Yellow Card Scheme was soon beginning to pay dividends. In early 1966, the YeUow Card Scheme had identified methyldopa as a cause of haemolytic anaemia and an appropriate advice was issued. Another success was the detection of a faulty batch of a particular product, which the manufacturer immediately withdrew, underlining the value of an efficient procedure for tracing a batch. During June 1967, the Committee distributed a leaflet on the use of aerosols in asthma. This was prompted by the death rate amongst asthmatic patients aged 5 to 34 years that had risen some 300% above the level in 1959-60 when such preparations were introduced. By September 1968, the rate had dropped to only 50% above that seen in 1959-60 despite sales having dropped only 20%. 

Thus, if a particle secondary oxidation product does not get partitioned efficiently into the condensed phase (i.e., KtmJ is small) or the available organic condensed phase for uptake of the semivolatile product is small, Eq. (LL) reduces to Y M(lE ,/fnlI1/ and the secondary organic aerosol yield is proportional to the amount of condensed phase available for uptake of the low-volatily gaseous products. On the other hand, if KomJ and M are large, Eq. (LL) becomes Y Ea, independent of the amount of condensed phase available for product uptake. 

For volume production of an aerosol fog of small particle size, on a large scale (suited to indoor use), the thermal aerosol fog generators appear to be very efficient. The Science Service experiments were mostly with this type. Two principal varieties have been developed. One discharges the insecticide solution or suspension as a relatively coarse spray into a jet of superheated steam delivered by a flash boiler of the tubular coil t3rpe. The other discharges that insecticide solution or suspension as a relatively coarse spray into a blast of hot gas emerging from a combustion chamber. The temperature is regulated by the controlled admixture of cold air. 

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