Liquid Flame Spray (LFS) is a specific gas phase synthesis method of nanoparticles. It has recently been used in producing e.g. antimicrobial nanoparticle coatings. However, nanoparticles include a potential health risk for humans when inhaled. One can use respirator masks to protect oneself from inhaling the nanoparticles. There are also devices that measure the number and active surface area concentration of particles in room air.

LFS is a flame based method for generating nanoparticles in gas phase. Several different flame methods are widely used in material synthesis. In this study our point is, however, to show that LFS can be used to generate a well defined test aerosol for devices measuring nanoparticles. The aim is to simply make a stable concentration of a test aerosol in room air or in an aerosol chamber. The test aerosol can then be used in instrument testing or even in toxicological experiments. LFS consists of a high-temperature H₂-O₂ flame. One of the combustion gases atomises the liquid precursor into the flame where it evaporates and eventually forms nanoparticles. Using LFS metal and metal oxide nanoparticles can be processed with the production rate in the order of g/min. In this study we produced ferric oxide, titanium dioxide and metallic silver nanoparticles.

A fume chamber and a small room were used as test aerosol generation chambers. These two spaces were filled with nanoparticles. We measured the nanoparticles using several aerosol measurement devices: Electrical Low Pressure Impactor (ELPI), Ultrafine Condensation Particle Counters (working fluids butanol and water, UF-CPC and UF Water-CPC, respectively), Scanning Mobility Particle Sizer (SMPS), Nanoparticle Surface Area Monitor (NSAM), Engine Exhaust Particle Sizer (EEPS) and a prototype of an industrial hygiene monitor based on the escaping current technology (ECT-sensor). All the instruments measured the same room aerosol. Using the measurement data we show that LFS can be widely used in nanoparticle test aerosol generation. In this study we generated a steady distribution of nanoparticles ranging from 5 to 60 nm with surface area concentrations from 1 to 10000 μm²/cm³ in the room air. We also show that a bimodal distribution can be generated using the same or two different materials.