The purpose of the neutralizer is to impart a known, equilibrium charge distribution to the sampled polydisperse particles so that the DMA selects charged particles as a function of size in a known, repeatable manner. The DMA only selects charged particles, so a repeatable and robust technique for charging the incoming particles is critical to proper sizing with the DMA. The neutralizer can also be used to reduce particle losses in aerosol generation systems due to electrostatic precipitation. A photo of the disassembled neutralizer is provided in Figure 5. Under normal conditions, the vast majority of ambient particles carry no charge; some 1–25% carry a single charge with smaller number fractions of particles carrying multiple charges. However, the distribution of particles with one, two or more charges with particle size is not typically known unless they are exposed to ions of su?cient concentration so that a known distribution of charge is imparted to them. In some cases however, for example during electrical storms or when sampling atomized aerosol, a signi?cant fraction of the aerosol can be charged with an unknown distribution of charge as a function of particle size. The charging e?ciency of particles is a strong function of particle size, especially for particle diameters smaller than 100 nm. The ion source of the neutralizer consists of two radioactive Polonium-210 strips (0.5 mCi each, Model 2U500, NRD LLC, Grand Island, NY, Tel: 800-525-8076) that emit alpha particle radiation that ionize the air molecules near the strips. The half-life of Po-210 is 138.4 days. The range of the alpha particles in air is 3.8 cm and the radiation is incapable of penetrating the stainless steel body of the neutralizer. In fact, the alpha particles cannot penetrate the layer of dead skin (50 micrometers thick) on the human body. The sources used in the neutralizer do not require special handling precautions beyond those described in the NRD LLC technical literature.

氣溶膠中和器的目的是賦予采樣的多分散顆粒已知的平衡電荷分布，使得DMA以已知的可重復(fù)的方式選擇帶電粒子作為尺寸的函數(shù)。 DMA僅選擇帶電粒子，因此用于對(duì)進(jìn)入的粒子充電的可重復(fù)且穩(wěn)健的技術(shù)對(duì)于使用DMA進(jìn)行適當(dāng)?shù)某叽缯{(diào)整是至關(guān)重要的。氣溶膠中和器還可用于減少由于靜電沉淀引起的氣溶膠生成系統(tǒng)中的顆粒損失。圖5中提供了拆卸氣溶膠中和器的照片。在正常條件下，絕大多數(shù)環(huán)境顆粒不帶電荷;約1-25％攜帶一次充電，較少數(shù)量的顆粒帶有多個(gè)電荷。然而，具有一種，兩種或更多種帶粒徑的電荷的粒子的分布通常是未知的，除非它們暴露于足夠濃度的離子，從而賦予它們已知的電荷分布。然而，在某些情況下，例如在電風(fēng)暴期間或當(dāng)采樣霧化氣溶膠時(shí)，氣溶膠的顯著部分可以帶有未知的電荷分布作為粒度的函數(shù)。顆粒的充電效率是顆粒尺寸的強(qiáng)函數(shù)，特別是對(duì)于小于100nm的顆粒直徑。氣溶膠中和器的離子源由兩個(gè)放射性Pol -210條帶（每個(gè)0.5 mCi，型號(hào)2U500，NRD LLC，Grand Island，NY，電話：800-525-8076）組成，它們發(fā)射α粒子輻射，電離附近的空氣分子。 Po-210的半衰期為138.4天。空氣中α粒子的范圍是3.8厘米，并且輻射不能穿透氣溶膠中和器的不銹鋼體。事實(shí)上，α粒子不能穿透人體上的死皮層（50微米厚）。氣溶膠中和器中使用的來(lái)源不需要超出NRD LLC技術(shù)文獻(xiàn)中描述的特殊處理預(yù)防措施。