Sell that House!

Have you ever walked into an open house and been asked to take your shoes off?  The realtor’s top priority is to sell the house and, in order to do that, they should keep it as clean as possible.  They’re far more likely to sell it faster and for the most money if it is clean and in the best shape.

Let’s face it: our shoes are dirty!  The usual suspects like dirt, leaves, mud, gum, sap, and a variety of disgusting things can get all over the floor.  Some shoes also scuff up the floor so the realtor has to spend valuable time cleaning after everyone leaves.  No wonder that as soon as you walk into the house for sale you may be asked to remove your shoes.

Picture this: you crouch down in front of strangers and spend a minute unlacing your shoes and adding them to the fleet of other peoples’ shoes.  Alternatively, maybe you try to balance on one leg while taking each shoe off, successfully or perhaps not so much.  Or maybe you put your hand on the wall for balance, thereby leaving a hand print.  Then you walk around the house in your (dirty?) socks, which can be quite awkward with other people around.  Plus, you can’t walk to the backyard or outside at all because your socks will get dirty (dirtier?) and then you’ll track dirt back into the house.  When leaving you have to do the reverse process: more time, more balancing acts, more hand prints on walls.

Does it have to be this way?

Assortment of shoe covers on shoesOf course not.  The solution?  Shoe covers.  You can simply have visitors put them over their shoes and the floors won’t get dirty, scuffed or scratched.  Unfortunately, there is a catch: regular shoe covers can be difficult to put on and you still have the issue of finding a place to sit down or balancing or leaning on a wall.  This can create a bit of a traffic jam at the entrance and cause people to get impatient.

This is why Shoe Inn provides automatic shoe cover dispensers, which make it faster, easier, safer and cleaner to put shoe covers on.  Nobody has to sit down, balance precariously while trying to avoid falling, leave hand prints on walls, or walk around in their socks.  Visitors will be much happier, sufficiently impressed, and more apt to buy the home.

Get your automatic shoe cover dispenser here today!

Cleanrooms

Cleanroom scientists wearing shoe coversCleanrooms (or clean rooms) are used in virtually every industry where small particles can adversely affect the manufacturing process.  Typically located in scientific research or manufacturing settings, a cleanroom is a controlled environment that has a controlled level of contamination (pollutants such as dust, airborne microbes, chemical vapors, and aerosol particles) that is specified by the number of particles per cubic meter (m3) or per cubic foot (ft3) at a specified particle size.  Believe it or not, the ambient air outside in a typical city environment contains about 35,000,000 particles per m3, 0.5 μm and larger in diameter, which corresponds to an ISO 9 cleanroom.  At the other end of the spectrum, an ISO 1 cleanroom allows no particles in that size range and only 12 particles per m3 of 0.3 μm and smaller.

Cleanroom Overview

A cleanroom is any given contained space where provisions are made to reduce particulate contamination and control other environmental parameters such as pressure, temperature, and humidity. The key component is the HEPA (High Efficiency Particulate Air) filter that is used to trap 99.97% of particles that are 0.3 microns and larger in size. All of the air delivered to a cleanroom passes through HEPA filters, and in cases where more stringent cleanliness performance is necessary, ULPA (Ultra Low Particulate Air) filters are employed.

The use of multi-layer adhesive mats for cleanrooms is almost universal.  Matting can vary in size, color, placement, and number based on the characteristics and logistics of each individual cleanroom.

Personnel who work in cleanrooms go through extensive training in contamination control theory, practices and procedures. They enter and exit the cleanroom through air showers, airlocks, and/or gowning rooms, and they must wear special clothing designed to trap contaminants that are naturally generated by our bodies.

Depending on the room classification or function, personnel gowning may be as limited as lab coats and hairnets/beard covers, or as extensive as being fully enveloped in multiple layered bunny suits with self-contained breathing apparatus.  The cleanroom clothing itself must not release fibers or particles to prevent contamination of the environment.

Cleanroom garments include things such as boots, shoes, shoe covers, beard covers, hairnets, bouffant caps, facemasks, coveralls, aprons, frocks/lab coats, gowns, glove and finger cots, hoods, and sleeves. The type of cleanroom garments used reflects the cleanroom classification and product specifications. For example, Class 10,000/ISO 7 cleanrooms may use simple smocks, head covers, and shoe covers.  On the other hand, careful gown wearing procedures with a zipped coverall, boots, gloves and complete respirator enclosure are required for Class 10/ISO 4 cleanrooms.

Cleanroom technicians wearing shoe covers
Cleanroom technicians wearing shoe covers

Air Flow Principles for Cleanrooms

Cleanrooms maintain particulate-free air through the use of either HEPA or ULPA filters employing laminar or turbulent air flow principles. Laminar, or unidirectional, airflow systems direct filtered air downward in a constant stream. Laminar airflow systems are typically employed across 80% to 100% of the ceiling to maintain constant air processing and unidirectional flow. Laminar flow criteria are mandated in ISO 1 through ISO 4 cleanrooms.  Turbulent, or non-unidirectional, air flow uses both laminar air flow hoods and non-specific velocity filters to keep cleanroom air in constant motion, although not all in the same direction. The rough air seeks to trap particles that may be in the air and drive them towards the floor, where they enter filters and leave the controlled environment.

Proper cleanroom design encompasses the entire air distribution system, including provisions for adequate downstream air returns. In horizontal flow applications, this involves the use of air returns at the downstream boundary of the process.  In vertical flow rooms, it requires the use of low wall air returns around the perimeter of the zone.  It should be noted that the use of ceiling mounted air returns is contradictory to proper cleanroom system design.

Cleanroom Classifications

Cleanrooms are classified by how clean the air is according to the number and size of particles permitted per volume of air. Federal Standard 209E is used here in the U.S.  The newer standard is TC 209 from the ISO (International Standards Organization).  Both standards classify a cleanroom by the number of particles found in the laboratory’s air. The cleanroom classification standards 209E and ISO 14644-1 require specific particle count measurements and calculations to classify the cleanliness level of a cleanroom or clean area.

Large numbers like Class 1,000 or Class 100,000 refer to FS 209E, and denote the number of particles of size 0.5 µm or larger permitted per ftof air. The standard also allows interpolation, so it is possible to describe other classes such as Class 2,000.

Small numbers refer to ISO 14644-1 standards, which specify the decimal logarithm of the number of particles 0.1 µm or larger permitted per mof air.  For example, an ISO 4 cleanroom has at most 104 = 10,000 particles per m³.

Both FS 209E and ISO 14644-1 assume log-log relationships between particle size and particle concentration. For that reason, there is no such thing as zero particle concentration.

US FED STD 209E cleanroom standards

Class Maximum particles/ft3 ISO equivalent
≥0.1 µm ≥0.2 µm ≥0.3 µm ≥0.5 µm ≥5 µm
1 35 7.5 3 1 0.007 ISO 3
10 350 75 30 10 0.07 ISO 4
100 3,500 750 300 100 0.7 ISO 5
1,000 35,000 7,500 3,000 1,000 7 ISO 6
10,000 350,000 75,000 30,000 10,000 70 ISO 7
100,000 3.5 x 106 750,000 300,000 100,000 700 ISO 8

ISO 14644-1 cleanroom standards

Class Maximum particles/m3 STD 209E equivalent
≥0.1 µm ≥0.2 µm ≥0.3 µm ≥0.5 µm ≥1 µm ≥5 µm
ISO 1 10 2.37 1.02 0.35 0.083 0.0029
ISO 2 100 23.7 10.2 3.5 0.83 0.029
ISO 3 1,000 237 102 35 8.3 0.29 Class 1
ISO 4 10,000 2,370 1,020 352 83 2.9 Class 10
ISO 5 100,000 23,700 10,200 3,520 832 29 Class 100
ISO 6 1.0 x 106 237,000 102,000 35,200 8,320 293 Class 1,000
ISO 7 1.0 x 107 2.37 x 106 1,020,000 352,000 83,200 2,930 Class 10,000
ISO 8 1.0 x 108 2.37 x 107 1.02 x 107 3,520,000 832,000 29,300 Class 100,000
ISO 9 1.0 x 109 2.37 x 108 1.02 x 108 35,200,000 8,320,000 293,000 Room air

How to Transition from ‘Dirty’ to ‘Clean’ While Booting Up in a Gowning Room

Prior to entering a cleanroom, employees need to get “gowned up” in special clothing designed to trap contaminants that are naturally generated by our bodies.  Depending on the room classification or function, personnel gowning may be as limited as hairnets/beard covers and lab coats, or as extensive as being fully enveloped in multiple layered bunny suits with self-contained breathing apparatus.

The Gowning Room

cleanroom-gowning-area-600

Cleanroom personnel generally “boot up” in dedicated shoes or shoe covers, and in order to make sure they don’t get contaminants on the shoe covers before entering the cleanroom, they typically follow a transition protocol from the “dirty” to the “clean” side of the floor/room.  This usually entails a gowning bench or chair placed along a line that has been taped or painted on the floor, or along the line between two different colored floor tiles.  While sitting, the employee puts the first shoe cover on, puts that foot down on the “clean” side, then repeats the action for the second foot.  Sometimes regular shoe covers tear while being put on, so the employee has to take them off, throw them away, and start the process over again.

A much easier, safer, and faster way of putting shoe covers on is to use a Shoe Inn automatic shoe cover dispenser.  These dispensers are similarly placed along the line between the “dirty” and “clean” parts of the floor.  In this setup, while standing on the “dirty” side, the employee puts the first shoe cover on, puts that foot down on the “clean” side, then repeats the action with the second foot and proceeds to the next step in the gowning process.  Because the employee does not have to go grab precisely two shoe covers, walk to the bench, sit down, put the shoe covers on, and stand back up, not to mention not having to deal with improperly sized and torn shoe covers, the “booting up” process is much more efficient, which can help alleviate gowning room bottlenecks and significantly improve productivity.