CleanRoom-SmokeStudies

Liquid Nitrogen foggers are quite effective in producing a visible fog to visualize airflow patterns, airflow uniformity. Also referred to as an LN2 fogger and ultrapure fogger, these foggers came into use in the early 2000 time frame in smoke studies, replacing smoke sticks and CO2 fog pots. Smoke sticks, by definition, produce a smoke, which is chemical/heat induced smoke composed of particulate smoke. In modern ISO Suites and Cleanrooms, smoke sticks would be banned by most Metrology Engineers in 2025. CO2 fog is produced by producing CO2 ice, and dropping it into a warm water bath, allowing the CO2 to evaporate and combine with water vapor to form a dense fog. Yet a CO2 fog, although rather simple to produce, does not allow for volume control or velocity control, as do more recent fogger technology. 

Since 2015, more useful fogger technology has been put into use, referred to as DI Water Foggers, Portable foggers and ultrapure cleanroom foggers. The more recent fogger technology incorporates fog volume control, velocity control of the fog output and wireless remote control, all which are important control elements to evaluate the airflow performance in a smoke study.

Of these different foggers, the LN2 foggers produce the most fog density and fog volume for smoke studies; while ultrasonic foggers produce the less fog, they are easier to operate and set up for operation in a smoke study. The four ultrapure LN2 foggers compared above are the AP35, AP50, AP100 and AP150. Each of these foggers operate the same with velocity control, water temperature control and fog volume control; the only difference being the volume of the LN2 Dewar at 35 L, 50 L, 100 L or 150 liters.

For discussion, we will refer to the AP35 LN2 ultrapure fogger, which produces about 5 cubic meters ultrapure fog per minute, and includes a rolling trolley for easy movement around a clean room or ISO Suite. It uses 11.5 liters water and 35 liters LN2 to produce fog over a typical 45 minute fog cycle. The AP35 provides adjustable fog volume, adjustable fog velocity, and it also includes an optional wireless remote control Key FOB. The AP35 produces an ultrapure fog at about 2-3 micron fog droplet diameter with very high fog density, where as the typical ultrasonic fogger produces larger fog droplets from 5 to 8 microns but at much lower fog density. The AP35 Ultrapure Fogger can visualize airflow turbulence and balance airflow between rooms. The Ultrapure fog is generated by heating water to form water vapor, and then allowing nitrogen vapor to combine with the water vapor to form a very dense fog at much smaller droplet diameters.  Water vapor combined with Nitrogen vapor forms a 2-3 micron diameter fog vapor droplet. LN2 readily boils at room temperatures, producing high volume of nitrogen vapor. The older LN2 foggers of 2001 vintage had no adjustable controls, which is why the older foggers are being replaced with newer LN2 fogger technology with adjustable controls, making the AP35, AP50, AP100 and AP150 very effective tools in smoke studies in ISO Suites and clean rooms.

The chart above compares the foggers used today in smoke studies around the world. The SMST-12 is the lower cost, entry level fogger, and used in small volumetric smoke studies such as 2×4′ airflow hoods and in fume hood airflow studies. As you go down the table, each fogger shows performance attributes, which help metrology engineers and airflow technicians identify the fogger that best supports their smoke study requirements.

The ultrasonic fogger with the highest fog volume per minute is the AFM40 Cleanroom Fogger, also marketed as the CRF6 Cleanroom Fogger. It is a very effective portable fogger, quick to set up for a smoke study and has two 80mm fog outlets so that a maximum amount of pure fog is emitted for a typical smoke study in a barrier isolator or small ISO Suite airflow visualization test.  The AP35 is the next step up if fog volume, fog density and fog purity, followed by the AP50, AP100 and AP150. All of the AP series Ultrapure Foggers use DI (de-ionized) water, WFI (water for injection) or sterile water; and also uses LN2 to produce an ultrapure fog. The AP35 uses 35 liters LN2, the AP50 uses 50 liters LN2, AP100 uses 100 liters of LN2, while the AP150 uses 150 liters of LN2. Each of these foggers provide a Control Unit, that includes a 13.5 liter water cavity, combined with water temperature control and fog velocity control and fog volume control.

The higher the fog density, the more visual fog distance is provided, and our AP35 provides 2 times more fog density than our best CRF6 Cleanroom Fogger. Our ultrapure foggers produce the highest fog volumes with the most fog purity, combined with useful accessories to conduct smoke studies in your clean rooms and ISO suites. The AP100 LN2 Ultrapure Fogger produces 16 cubic meters a minute of ultrapure fog and provides two 5M x 80mm fog outlets, while the AP150 provides up to 24 cubic meters of ultrapure fog per minute and offers three 80mm fog outlets. hose outputs. Our LN2 foggers are designed for high volume, ultrapure fog with controllable fog output and 12 different accessories for use in a smoke study.

Some companies and engineers do not want to use LN2, or do not have access to LN2. If you do not want to use LN2, but want high volume fog, consider the CRF6 Cleanroom Fogger, also marketed as the AFM40 Cleanroom Fogger. The CRF6 and AFM40 provides about 2 cubic meters of pure fog per minute for about35-40 minutes through two 80mm fog outlets, providing 13-15 feet of visual airflow using the appropriate fog wands and 80mm hoses. It provides an adjustable fog volume and airflow velocity, touch pad control and wireless remote control. Alternatively, we provide our SMST-12 Smoke Studies Fogger for low cost solutions to provide airflow visualization in 2×4′ fume hoods, Bio-Safety Cabinets and Aseptic Isolators. Our foggers are priced according to fog volume produced. 

It does not make sense to buy a smoke generator unless you match the fog output to your smoke study requirements. If you do not know how much fog volume is needed for a smoke study, and if you have varying requirements for fog volume, consider the CRF6 or CRF4 Cleanroom Foggers. These foggers use ultrasonics to produce fog, thus have a simple set up sequence to conduct a smoke study. rflow distance provided. Use De-ionized water, Distilled water, WFI water or sterile water, or any pure pharmaceutical water. DI water foggers are more simple to operate but produce less fog and fog density than our ultrapure foggers. Our SMST-12 Cleanroom Fogger support airflow visualization and airflow recovery tests as defined by ISO 14644-3, B12. The CRF6 Cleanroom Fogger is ideal for airflow visualization in clean rooms, ISO suites, medical operating rooms and sterile rooms. Contact Applied Metrology LLC at TEL: 1-720-635-3931 or 1-303-999-6837.