Contamination in the workplace can halt production, necessitate expensive product recalls, or require lab experiments to be started over. It is a very real concern, perhaps even a fear, that laboratories, food processing companies, and manufacturers are particularly aware of and have measures in place to minimize or prevent. In this post, we discuss what contamination is, how it can be spread, and what can be done to try to prevent it.
Contamination: what is it?
The definition of contamination is the act of contaminating, or of making something impure or unsuitable by contact with something unclean, poisonous, etc. One of the most publicly visible examples of the effects of contamination is widespread food borne illness leading to hospitalizations and deaths. Negative food safety headlines are the worst nightmare of food processing companies and restaurants. This issue is discussed further in our shoe covers in the food industry blog post.
How is it spread?
Contamination can be spread through a variety of ways, including through the air (think tiny infectious droplets spread by coughs and sneezes), water, food, touching unclean surfaces, etc. Workers who don’t correctly follow procedures can cause cross-contamination, thereby halting production, having to decontaminate or discard products, needing to clean equipment, and other effects that result in lost time and money.
What can your company do to be safe from contamination?
Companies minimize workplace contamination by developing, implementing, and enforcing proper processes and procedures (including disinfection and cleaning procedures), having necessary infrastructure and equipment, and the like. Personal protective equipment (PPE) is also an important consideration. By wearing shoe covers, hair nets, face masks, beard covers, and gloves, potential contaminants should be kept away from critical areas. The PPE will also help keep the work environment clean and sanitary.
Contamination is a very important matter, but you can lessen the likelihood of it occurring if you know what it is, how it spreads, and what can be done to minimize or prevent it entirely with cross-contamination prevention. Compliance with company processes and procedures is critical, as is having proper infrastructure and equipment, which may include shoe covers, disposable gloves, and sticky mats.
While many companies use shoe covers to prevent contamination, many Shoe Inn customers also use sticky mats to maximize contamination prevention. The utilization of multi-layer adhesive mats for cleanrooms is almost universal. However, how the mats are used is unique to each cleanroom. Mats can vary in size, color, number, and placement based on the logistics and characteristics of each individual cleanroom.
Mats should be placed in an area where they will be on clean, hard flooring. They should be placed just before or just after the ingress/egress point for each cleanliness or control change. It is suggested that the placement sites are worked backward from the final clean area or cleanroom.
cleanroom – gowning area
cleanroom – staging area
gowning area – control area
control area – common hallway
common hallway – warehouse or receiving
common hallway – public area
Matting should be placed so that all those passing through that point must step on the mats. Matting should be placed with the longer dimension of the mat in the same direction as the traffic flow for maximum footfalls on each mat. The minimum number of footfalls should be two with each foot for each location.
The proper size mat for each area of placement depends on the width of the opening and the variance and direction of the traffic. Normally the width of the mat should be 2/3rds to 3/4ths of the width of the doorway. It does not normally need to cover the full width because ordinary traffic passes through the middle of the doorway and not along the edge. However, if the traffic enters at a sharp angle or from the side of the entryway, then the width of the mat needs to be wider than the doorway to allow for enough footfalls.
As stated above, the length of the mat should be long enough to provide at least two footfalls with each foot at each location. Usually this is a minimum of 45 inches.
The color of the mats, which has no effect on the function of the mat, can vary from standard blue, white, and grey to custom colors and printed messages. In general, white shows the most dirt and particulates, and is normally preferred to make sure the layers are changed at frequent enough intervals. However, grey and blue work just as well when a maintenance schedule is set.
How often the layers should be removed depends on a number of factors:
How dirty the area the personnel are coming from is.
The number of people or pairs of feet per shift or per hour.
The difference in cleanliness between the areas.
The size of the mats and how many mats or locations are in the series.
In general, areas farther away from the cleanroom will be dirtier. Changing the layers at this point of use every half hour would be a benchmark with which to start. The final entry area into the cleanroom is probably from a clean area to a very clean area and each layer may last 4 to 8 hours.
However, this is just a rough guideline and each point of use will vary greatly. A few days of use and observation will help to determine the optimal mat layer change interval.
Before placing a new mat down or replacing an existing mat, thoroughly clean the surface to remove contamination that may act as a barrier and keep the mat from properly adhering to the floor. Make sure to remove any adhesive residue if you are replacing an existing mat. It is recommended to use a pre-saturated wiper that contains a percentage of isopropyl alcohol. Make sure the surface is completely dry before application.
To apply the mat, remove half of the release liner in the long direction of the mat, which will help with the alignment of the mat.
Once you have the mat properly aligned in the location you want, start smoothing out the half of the mat with the adhesive exposed. Start at one end and work toward the middle making sure you do not trap air under the mat as you go, then remove the rest of the release liner and smooth the rest of the mat out in the same direction in which you removed the release liner.
Matting should be stored flat and for several hours in similar climate conditions as the point of use. For ideal results, the mats should be used in a controlled environment setting but may be placed in any area that has a temperature of 54-95 oF (12-35 oC).
Long-term storage of mats should always be on a flat and hard surface. Storage on the original shipping pallet is recommended. Normal warehouse conditions are usually acceptable but extreme temperatures (less than 32 or greater than 105 oF / 0 or 40 oC) should be avoided.
Storage of mats longer than one year from the date of purchase is not recommended. However, under normal storage conditions, matting should not have any variation in performance for a period of up to three years.
The utilization of multi-layer sticky mats for cleanrooms is almost universal. In fact, many customers who use the Shoe Inn automatic shoe cover dispensing system also use these adhesive mats to further help prevent contamination within controlled environments. Depending on various factors such as how dirty the area the personnel are coming from is and the level of cleanliness desired or mandated, this combined approach may be advisable or even required.
Have you ever considered what is on the bottom of your shoes? Besides things you can see, such as grease, oil, gum, mud, leaves, feces, etc., there are the countless things you cannot see, like germs, bacteria, mold, and viruses. All of these things walk with us everywhere we go, from the house to the car to the parking lot to the building to the lab or production area to the bathroom to the dining area and back again. How many other places do we go, like gas stations and public parks, picking up things on our shoes all along the way and transporting them where they are unwelcome?
As a result, many industries and settings require the use of shoe covers to maintain sanitary or sterile conditions, prevent contamination, limit the spread of infections, comply with health codes, etc. A review of the literature turned up several key findings such as the following:
“In this study, the authors subjected six occupied rodent holding rooms in their animal research facility to three conditions: use of disinfectant mats; use of shoe covers; and no disinfectant mats or shoe covers. The authors took bacterial culture samples from the rooms under each condition. There was no significant difference in the mean number of colony forming units (CFUs) cultured when the disinfectant mats or shoe covers were used. However, the mean number of CFUs obtained was significantly lower when either disinfectant mats or shoe covers were used than when neither was used. These results suggest that using disinfectant mats or disposable shoe covers may reduce the bacterial load on rodent holding room floors.”
“We recommend that gloves and footwear worn by employees who handle RF-RTE foods or who work in areas where RF-RTE are processed or exposed be made of impermeable material, in good repair, easily cleanable or disposable (emphasis added), and used only in RF-RTE areas.”
“Health care workers who handle hazardous drugs are at risk of skin rashes, cancer and reproductive disorders. NIOSH recommends that employers provide appropriate personal protective equipment (PPE) to protect workers who handle hazardous drugs in the workplace…Use hair and shoe covers constructed of coated materials to reduce the possibility of particulate or microbial contamination in clean rooms and other sensitive areas.”
Based on the above, it is clear that using disposable shoe covers is a credible and recommended method in a variety of situations and controlled environments.
 Allen KP, Csida T, Leming J, Murray K, Thulin J. Efficacy of Footwear Disinfection and Shoe Cover Use in an Animal Research Facility, U.S. National Library of Medicine, http://www.ncbi.nlm.nih.gov/pubmed/20305633
 US Food and Drug Administration, Guidance for Industry: Control of Listeria monocytogenes in Refrigerated or Frozen Ready-To-Eat Foods, Section XI, Paragraph IV