JP5769462B2 - Decontamination condition determination method - Google Patents

Description

  The present invention relates to a decontamination condition determination method for determining an appropriate decontamination condition when decontamination is performed by generating a decontamination gas in a room such as an aseptic room, a clean room, or a hospital room.

  In a manufacturing site where pharmaceuticals or foods are manufactured, or in a medical site such as an operating room, it is important to maintain sterility in the room. In particular, in the decontamination of an aseptic room, which is a working room for pharmaceutical manufacturing, it is necessary to complete advanced decontamination validation in accordance with GMP (Good Manufacturing Practice).

  In recent years, hydrogen peroxide gas is being used for decontamination of a working room such as an aseptic room (hereinafter referred to as a decontamination target room) instead of formalin gas harmful to the human body. This hydrogen peroxide gas has a strong sterilization effect, is inexpensive and easily available, and is effective as an environmentally friendly decontamination gas that eventually decomposes into oxygen and water.

  It is described in the following Patent Document 1 that the decontamination effect by the hydrogen peroxide gas is due to a condensed film of hydrogen peroxide water condensed on the surface of the decontamination target site. Therefore, in order to achieve the perfect decontamination effect in the decontamination target chamber, the hydrogen peroxide solution condensed film generated by increasing the supply amount of the hydrogen peroxide gas may be made thick or high in concentration.

  However, if an excessive amount of hydrogen peroxide gas is supplied to the decontamination target chamber, excessive condensation occurs, and various manufacturing equipment and precision measuring equipment installed in the decontamination target chamber or the wall of the decontamination target chamber There is a problem that the high concentration hydrogen peroxide solution generated is corroded by the condensed film. Therefore, when hydrogen peroxide gas is used as the decontamination gas, it is particularly important to set advanced decontamination conditions in consideration of the relationship between the gas supply amount and the decontamination effect, as compared with the conventional decontamination gas.

  This decontamination condition is set by combining a number of parameters (hereinafter referred to as decontamination parameters) such as temperature, humidity, gas supply amount (total input amount, input speed, input time) of the decontamination target chamber, In order to obtain the above decontamination validation without the above-mentioned problems, it is important to appropriately evaluate the decontamination effect and determine an appropriate decontamination condition based on the result.

Japanese Patent Publication No.61-4543

  By the way, when the room to be decontaminated such as a sterile room is normally used, the air conditioner is operated to control the temperature and humidity in the room. On the other hand, when supplying the hydrogen peroxide gas into the room to perform decontamination in the room, the decontamination is started after the air conditioning equipment is stopped. Accordingly, the room temperature and humidity at the start of decontamination are set as decontamination parameters as initial conditions for starting decontamination.

  Here, since the decontamination target chamber has a large volume and various indoor shapes, there is a limit to the accuracy of the installed air conditioning equipment, and a certain control range is generated for temperature and humidity control. Therefore, even when one decontamination condition is configured by setting each decontamination parameter, the temperature and humidity of the initial condition fluctuate each time within a certain control range during actual decontamination. Therefore, in order to obtain advanced decontamination validation, even if the temperature and humidity of the initial conditions fluctuate within a certain control range, the sufficient decontamination effect that was initially planned must be exhibited.

  Therefore, in order to actually evaluate one decontamination condition, with the decontamination parameters other than temperature and humidity being fixed, the temperature control range of the air conditioning equipment and the combination of temperature and humidity corresponding to the humidity control range respectively. Conduct multiple decontamination tests. As a result, it is determined that only decontamination conditions that have been confirmed to exhibit a sufficient decontamination effect at any combination of temperature and humidity are effective decontamination conditions.

  However, performing a single decontamination test requires complicated and long work. Further, in order to evaluate one decontamination condition, as described above, a plurality of tests corresponding to the control width of the air conditioning equipment are required, and enormous time and cost are required. This has been a serious problem in evaluating decontamination conditions.

  Furthermore, in order to determine a decontamination condition appropriate for a certain decontamination target room, first, a number of decontamination parameters including temperature and humidity are changed, and a plurality of decontamination conditions are set in combination with each other. Next, individual decontamination conditions are evaluated to determine the most efficient decontamination conditions that maintain the required decontamination level and do not supply excessive hydrogen peroxide gas.

  Thus, in order to determine appropriate decontamination conditions for a certain decontamination target room, a plurality of possible decontamination conditions are set, and for each decontamination condition, temperature and humidity are respectively set. Multiple decontamination tests corresponding to the control width must be carried out.

  Therefore, the present invention addresses the above-mentioned problems and implements a decontamination test that requires enormous time and cost when adopting hydrogen peroxide gas to determine the appropriate decontamination conditions for the decontamination target room. The purpose of the present invention is to provide a decontamination condition determination method that can reduce the number of times and determine decontamination conditions that enable efficient and advanced decontamination validation from a plurality of decontamination conditions. To do.

  In solving the above problems, the present inventors repeated actual decontamination tests corresponding to the temperature control range and humidity control range of the air conditioning equipment, respectively. A correlation was found between the humidity and the decontamination effect, and the present invention was completed.

That is, according to the description of claim 1, the decontamination condition determination method according to the present invention,
In order to supply hydrogen peroxide gas to a decontamination target chamber equipped with a temperature / humidity control device and decontaminate the inside of the decontamination target chamber, an appropriate combination of a plurality of parameters including a temperature parameter and a relative humidity parameter A decontamination condition determination method for determining a decontamination condition,
A decontamination condition setting step of setting a plurality of decontamination conditions by changing at least one of the plurality of parameters constituting the decontamination conditions;
For each of the plurality of decontamination conditions, a decontamination test execution step for performing a decontamination test by installing a biological indicator for determining a decontamination effect at a predetermined position of the decontamination target chamber,
The decontamination effect of the decontamination test conforms to a predetermined standard from the logarithmic decrease in the number of bacteria achieved in each decontamination test obtained from the determination result of the biological indicator after the decontamination test execution step. A decontamination effect determination step for determining whether or not,
From the result of the decontamination effect determination step, it has a decontamination condition determination step for determining appropriate decontamination conditions for the decontamination target room,
In the decontamination test implementation process,
When the temperature parameter setting value is A (° C.) and the relative humidity parameter setting value is B (%) as an initial condition when starting the decontamination test, the temperature and humidity control device controls the indoor temperature range. [A-a1] (° C) to [A + a2] (° C) and can be controlled in the room relative humidity range [B-b1] (%) to [B + b2] (%)
In the combination of the indoor temperature range [A−a1] (° C.) to [A + a2] (° C.) and the indoor relative humidity range [B−b1] (%) to [B + b2] (%), the absolute humidity value is Only one temperature / humidity condition consisting of the combination of the lowest indoor temperature and room relative humidity is adopted as the initial condition, and the temperature / humidity control device is stopped after the temperature of the decontamination target room is set as the temperature / humidity condition. It is characterized by starting a test.

  According to the above configuration, the decontamination condition determination method includes a decontamination condition setting process, a decontamination test execution process, a decontamination effect determination process, and a decontamination condition determination process. In the decontamination condition setting step, various decontamination parameters are combined to decontaminate the decontamination target chamber with hydrogen peroxide gas, and a plurality of decontamination conditions that are considered appropriate are set. These set decontamination conditions are implemented in the subsequent decontamination test execution process, and it is compared which decontamination conditions are appropriate for the decontamination target room.

  Here, these decontamination parameters include the indoor temperature and humidity, the supply rate and supply time of the hydrogen peroxide gas, and are set by combining these. The room temperature and humidity are the initial conditions of the decontamination test, and the supply speed and supply time correspond to the supply amount of hydrogen peroxide gas. In particular, the supply speed and supply time of the latter hydrogen peroxide gas are factors controlled by the indoor decontamination apparatus that supplies the hydrogen peroxide gas.

  In the decontamination test execution process, the decontamination target room is actually decontaminated according to the decontamination conditions set in the decontamination condition setting process. The decontamination test is performed by determination using a biological indicator (hereinafter referred to as BI) that matches a desired decontamination level.

Here, the predetermined reference means, for example, whether or not a 4 to 6 log reduction (log reduction) is exhibited. For example, at a decontamination level of 6 log reduction, BI having 10 ⁶ sterilization indicator bacteria that are most resistant to the decontamination reagent to be used is installed at a plurality of locations in the decontamination target room. Do. Thereafter, this BI is collected and cultured, and it is determined that a 6 log reduction has been achieved when the sterilization indicator bacterium of the BI has completely died.

  In the decontamination effect determination step, the BI collected by the decontamination test is cultured by a predetermined method to determine the sterilization state. The decontamination effect of the decontamination test thus obtained is used in the subsequent decontamination condition determination step, and is used to determine the appropriate decontamination conditions for the decontamination target room.

  In the decontamination condition determination step, the sterilization state determined from the culture result of BI and the total supply amount of hydrogen peroxide gas calculated from the supply rate and supply time of the hydrogen peroxide gas among the decontamination parameters are considered. As a result, a decontamination condition that is not excessive supply of hydrogen peroxide gas, is efficient in work, and has a decontamination effect is determined.

  In the decontamination condition determination method performed as described above, a feature of the present invention resides in the decontamination test execution step. That is, when the setting value of the temperature parameter of the decontamination condition is A (° C.) and the setting value of the relative humidity parameter is B (%), the room temperature is [A-a1] depending on the control range of the temperature and humidity control device. The temperature fluctuates in the range of (° C.) to [A + a2] (° C.), and the indoor relative humidity fluctuates in the range of [B−b1] (%) to [B + b2] (%).

Therefore, in the present invention, in the combination of the indoor temperature range [A−a1] (° C.) to [A + a2] (° C.) and the indoor relative humidity range [B−b1] (%) to [B + b2] (%). Without performing the decontamination test under a plurality of temperature / humidity conditions , the decontamination test is performed only under one temperature / humidity condition of the combination of the temperature and the relative humidity at which the absolute humidity value becomes the smallest.

  This is because the decontamination test under the condition where the absolute humidity value is the smallest is the most difficult condition for decontamination. When the absolute humidity is larger, the decontamination effect becomes larger. It will be. Therefore, by performing the decontamination test only under the condition where the absolute humidity value is the minimum, an accurate decontamination effect can be achieved with the minimum number of times.

  Therefore, in the first aspect of the present invention, when hydrogen peroxide gas is used to determine the appropriate decontamination conditions for the decontamination target room, the number of decontamination tests that require enormous time and cost is reduced. Therefore, it is possible to provide a decontamination condition determination method capable of determining a decontamination condition that enables efficient and advanced decontamination validation from among a plurality of decontamination conditions.

It is a correlation figure which shows the relationship between room temperature (degreeC) and D value (minute) in an initial condition. It is a correlation diagram which shows the relationship between indoor relative humidity (%) and D value (minute) in an initial condition. It is a correlation diagram which shows the relationship between indoor absolute volume humidity (g / m < ³ >) and D value (minute) in an initial condition.

Hereinafter, in describing the decontamination condition determination method according to the present invention, first, the decontamination test conducted by the present inventors and the analysis of the decontamination effect will be described. This decontamination test was conducted to deal with the control range of temperature and relative humidity by the air conditioning equipment, and was carried out with fixing decontamination parameters other than temperature, relative humidity and exposure time.
〔Test method〕
(1) Decontamination environment Using a room decontamination apparatus (Japanese Patent Application Laid-Open No. 2009-273645) according to the inventors' invention for a decontamination target room having a volume of 60 m ³ equipped with air conditioning equipment A decontamination test with hydrogen gas was performed.

(2) Setting of initial conditions The actual decontamination test is started after the air conditioning equipment in the room to be decontaminated is operated and the air conditioning equipment is stopped in a state where the indoor temperature and relative humidity are stable. The measured values of the indoor temperature and relative humidity when the air conditioning equipment was stopped were used as initial conditions. As the initial conditions, the room temperature was set to three levels of 24 ° C., 26 ° C., and 28 ° C., and the initial conditions were set by changing the relative humidity conditions for these room temperatures. In this decontamination test, eight sets of initial conditions were set in which the relative humidity was changed in the range of 34% to 64% (see Table 1).

  With respect to these eight sets of initial conditions, a decontamination test was performed according to the following procedures (3) to (8).

(3) Installation of BI The number of 6 log reduction BIs required for the decontamination test was set at a predetermined position in the decontamination target room.

(4) Start of generation of hydrogen peroxide gas When the measured values of indoor temperature and relative humidity reached the initial conditions set, the air conditioning equipment was stopped and the generation of hydrogen peroxide gas was started. Of the decontamination parameters other than the initial conditions of temperature and relative humidity, the supply amount of the hydrogen peroxide gas was set by the input rate and the input time of the hydrogen peroxide gas. The injection rate of the hydrogen peroxide gas is set by the generation amount of the hydrogen peroxide gas released into the decontamination target room per unit time, and specifically, 35% hydrogen peroxide dropped on the hydrogen peroxide gas generator. The water dropping rate was fixed at 1.5 g / min. In addition, the hydrogen peroxide gas was charged at five levels of 60 minutes, 120 minutes, 180 minutes, 240 minutes, and 300 minutes.

(5) Recovery of BI BI was recovered every 60 minutes from the start of generation of hydrogen peroxide gas. Therefore, the exposure time of the hydrogen peroxide gas to BI was 60 minutes, 120 minutes, 180 minutes, 240 minutes, and 300 minutes corresponding to the charging time.

(6) Culture of BI The recovered 6-log reduction BI was cultured by a predetermined method to determine the degree of sterilization.

(7) Indoor aeration After all the BIs were collected after 300 minutes had elapsed, indoor aeration was performed for 360 minutes in order to remove the hydrogen peroxide gas in the decontamination target chamber.

(8) Calculate D value based on determination of BI For evaluation of the decontamination effect, D value (Decimal reduction value) was adopted. The D value means the time (minutes) required to reduce the initial number of bacteria to 1/10 (90% death) under certain decontamination conditions. For the calculation of the D value, a method by LSKM (Limited Spearman-carber Method) using the culture result of the above 6 log reduction BI was adopted.
[Analysis of test results]
Table 1 shows the D values calculated from the initial conditions and the culture results for the eight decontamination tests performed by the above test method.

Using the D value obtained in Table 1, the relationship between the room temperature or the relative humidity in the room under the initial conditions and the D value was analyzed.

(1) Relationship Between Temperature and D Value FIG. 1 shows the relationship between the room temperature (° C.) and the D value (minute) under the initial conditions obtained from Table 1. In FIG. 1, each measurement point can be roughly divided into two groups according to relative humidity. That is, it is divided into a group T1 having a relative humidity of 40% and a group T2 having a relative humidity of 60%. Here, in the group T1, it is recognized that the D value tends to gradually become smaller as the temperature increases. On the other hand, in the group T2, a particularly clear correlation is not recognized. From this, in the decontamination of the decontamination target room having a control range in relative humidity, it was impossible to find a correlation between the room temperature and the D value.

(2) Relationship Between Relative Humidity and D Value Similarly, FIG. 2 shows the relationship between indoor relative humidity (%) and D value (minutes) under the initial conditions obtained from Table 1. In FIG. 2, each measurement point can be roughly divided into two groups according to relative humidity. That is, it is divided into a group H1 having a relative humidity of 40% and a group H2 having a relative humidity of 60%. Here, in any of the group H1 and the group H2, no correlation between the relative humidity and the D value could be found.

(3) Relationship between absolute humidity and D value Next, the absolute humidity was determined from the temperature and relative humidity under the initial conditions using a humid air diagram. Here, volume absolute humidity (g / m ³ ) was used as absolute humidity. Table 2 shows the absolute volumetric humidity (g / m ³ ) and the D value (min) determined.

FIG. 3 shows the relationship between the indoor absolute humidity (g / m ³ ) and the D value (min) under the initial conditions obtained from Table 2. In FIG. 3, the D value gradually takes a small value as the absolute humidity increases, indicating that the decontamination effect is improved.

From the above, in order to complete advanced decontamination validation in an environment where the accuracy of air conditioning equipment is limited and there is a certain control range for indoor temperature and relative humidity, focus on the absolute humidity in the room. It turns out that is important.
[Conventional decontamination condition determination method]
Here, an example of a decontamination condition determination method that has been conventionally performed to determine the decontamination conditions of the decontamination target chamber will be described. For example, the room temperature, the room relative humidity, the hydrogen peroxide gas charging speed, and the hydrogen peroxide gas charging time are set as the decontamination parameters. All other conditions are constant.

  Among the decontamination parameters, the hydrogen peroxide gas charging time can be dealt with by changing the exposure time in the same environment when other decontamination parameters are the same. Therefore, if the room temperature, the room relative humidity, and the hydrogen peroxide gas charging speed are fixed, it is considered that a single decontamination test may be performed.

  However, in practice, as described above, a plurality of tests in which temperature and relative humidity are combined in accordance with the control range of the air conditioning equipment must be performed. Furthermore, in order to complete advanced decontamination validation, it is required to perform decontamination tests under the same conditions at least three times.

  Assuming that the indoor temperature is 21 ° C. and the control width is ± 2 ° C., the indoor relative humidity is 45% and the control width is ± 5%. In this case, in the conventional decontamination condition determination method, at least four conditions of (19 ° C./40%), (19 ° C./50%), (23 ° C./40%), (23 ° C./50%) are used. It was necessary to conduct a decontamination test. Furthermore, when the test was repeated three times for each condition, a total of 12 decontamination tests were performed.

  On the other hand, according to the above findings of the present inventors, the decontamination test is performed only with the combination of the temperature and the relative humidity at which the absolute humidity value becomes the smallest among the combinations of the temperature control width and the relative humidity control width. Thus, the decontamination conditions can be evaluated without performing a plurality of decontamination tests. In the above example, it is sufficient to perform three times under one condition, and the number of decontamination tests that conventionally required 12 times is three.

Hereinafter, a decontamination condition determination method according to the present invention will be described based on embodiments.
[Embodiment of the present invention]
In the present embodiment, the indoor decontamination apparatus (Japanese Patent Application Laid-Open No. 2009-273645) according to the inventors' invention is installed in a 60 m ³ decontamination target room equipped with air conditioning equipment, and peroxidation is performed. Appropriate decontamination conditions were determined for the decontamination target room using hydrogen gas.

(1) Decontamination condition setting step The decontamination parameters set the room temperature and relative humidity in the room as initial conditions, and the charging speed and charging time as the hydrogen peroxide gas supply amount. Is shown in Table 3.

In this embodiment, as shown in Table 3, the decontamination parameters of the indoor temperature and the indoor relative humidity are set at one level, respectively, and the decontamination parameter of the hydrogen peroxide gas input rate is set at three levels. . Furthermore, the decontamination parameter of the hydrogen peroxide gas charging time was set at one level with 300 minutes.

  Therefore, in the present embodiment, according to the conventional decontamination condition determination method, a decontamination test of (3 setting conditions × 4 temperature / humidity conditions) × 3 times = 36 times is required. Then, it was impossible to actually carry out.

(2) Decontamination test implementation process As shown in Table 3, the temperature has a control width of 21 ° C. ± 2 ° C., and the relative humidity has a control width of 45% ± 5%. Therefore, in the present embodiment, first, the absolute volume humidity was determined for each combination of a temperature of 19 ° C. to 23 ° C. and a relative humidity of 40% to 50% using a wet air diagram. As a result, the absolute humidity value was the smallest at a temperature of 19 ° C. and a relative humidity of 40%, which was 6.5 g / m ³ . As a result, in this embodiment, under the initial conditions of a temperature of 19 ° C. and a relative humidity of 40%, three conditions of decontamination tests were performed by changing the hydrogen peroxide gas input rate.

  Therefore, No. in Table 3 The decontamination test was conducted under the condition of 1. First, in order to confirm the decontamination effect, 6 log reduction BIs were set at 40 locations in the decontamination target room.

  In this state, the air conditioning equipment in the decontamination target room was operated to adjust the room temperature and relative humidity. The measured value was 19 ° C. and the relative humidity was 40%. The air conditioning equipment was stopped in a stable state, and the decontamination test was started. As shown in Table 3, the dropping rate of 35% hydrogen peroxide dropped to the hydrogen peroxide gas generator was 1.0 g / min.

  After 300 minutes have elapsed since the start of the generation of hydrogen peroxide gas, the supply of the hydrogen peroxide gas is stopped, and the indoor aeration is performed in order to remove the hydrogen peroxide gas in the decontamination target chamber. I went for a minute. Thereafter, all BIs were collected and the decontamination test was completed.

  Here, in order to complete advanced decontamination validation, it is required to perform a decontamination test under the same conditions three times. Therefore, the same decontamination test as described above was further performed twice.

  Next, in the same manner, no. The decontamination test was conducted under the conditions of 2. In this decontamination test, the temperature and relative humidity in the room to be decontaminated are measured values of 19 ° C. and relative humidity 40%. As shown in Table 3, it was 1.5 g / min. The other conditions are No. This was the same as the 1 decontamination test. In addition, the same decontamination test was performed twice in order to complete advanced decontamination validation.

  Next, in the same manner, no. The decontamination test was conducted under the condition of 3. In this decontamination test, the temperature and relative humidity in the room to be decontaminated are actually measured at a temperature of 19 ° C. and a relative humidity of 40%, and the dropping rate of 35% hydrogen peroxide water dropped on the hydrogen peroxide gas generator is as follows: As shown in Table 3, it was 2.0 g / min. The other conditions are No. This was the same as the 1 decontamination test. In addition, the same decontamination test was performed twice in order to complete advanced decontamination validation.

(3) Decontamination effect determination step BI collected in each decontamination test was cultured by a predetermined method to determine the degree of sterilization. In the present embodiment, the used BI was for 6 log reduction, and the condition in which all of the collected sterilization indicator bacteria of all the BIs were completely killed was determined as having achieved 6 log reduction.

(4) Decontamination condition determination step From the above results, 1-No. Among the 3 decontamination conditions, appropriate decontamination conditions for decontamination with a 6 log reduction were determined for the decontamination target chamber of this embodiment. That is, in the decontamination conditions exhibiting the decontamination effect of 6 log reduction, the conditions with the smallest total amount of hydrogen peroxide gas were selected. Under these decontamination conditions, even if the room temperature fluctuates within the range of 19 ° C to 23 ° C, and the relative humidity fluctuates within the range of 40% to 50%, the decontamination always reduces by 6 logs. Can be guaranteed.

  Thus, conventionally, as described above, the number of decontamination tests requiring at least (3 setting conditions × 4 temperature / humidity conditions) × 3 times = 36 times is 3 conditions × 3 times = 9 times. It was possible to do it and became realistic. As a result, in consideration of the supply amount of hydrogen peroxide gas that can guarantee a 6 log reduction for each decontamination condition, various manufacturing facilities and precision measuring instruments installed in the decontamination target chamber or decontamination It was possible to determine the decontamination conditions with the least risk of causing the problem that the wall of the room to be dyed is corroded by the condensed film of high-concentration hydrogen peroxide.

  Therefore, in this embodiment, it is possible to reduce the number of decontamination tests that require enormous time and cost when using hydrogen peroxide gas to determine the proper decontamination conditions for the decontamination target room. In addition, it is possible to provide a decontamination condition determination method capable of determining a decontamination condition that enables efficient and advanced decontamination validation from a plurality of decontamination conditions.

Claims (1)

In order to supply hydrogen peroxide gas to a decontamination target chamber equipped with a temperature / humidity control device and decontaminate the inside of the decontamination target chamber, an appropriate combination of a plurality of parameters including a temperature parameter and a relative humidity parameter A decontamination condition determination method for determining a decontamination condition,
A decontamination condition setting step of setting a plurality of decontamination conditions by changing at least one of the plurality of parameters constituting the decontamination conditions;
For each of the plurality of decontamination conditions, a decontamination test execution step for performing each decontamination test by installing a biological indicator for determining a decontamination effect at a predetermined position of the decontamination target chamber,
The decontamination effect of the decontamination test meets a predetermined standard from the logarithmic decrease in the number of bacteria achieved in each decontamination test obtained from the determination result of the biological indicator after the decontamination test execution step. A decontamination effect determination step for determining whether or not,
From the result of the decontamination effect determination step, it has a decontamination condition determination step for determining an appropriate decontamination condition for the decontamination target room,
In the decontamination test execution step,
When the temperature parameter setting value is A (° C.) and the relative humidity parameter setting value is B (%) as an initial condition when starting the decontamination test, the temperature and humidity control device controls the indoor temperature range. [A-a1] (° C) to [A + a2] (° C) and can be controlled in the room relative humidity range [B-b1] (%) to [B + b2] (%)
In combination with the indoor temperature range [A-a1] (℃) to [A + a2] (℃) and the indoor relative humidity range [B-b1] (%) to [B + b2] (%), absolute humidity value Only one temperature / humidity condition consisting of a combination of the room temperature and the room relative humidity at which the temperature becomes the smallest is adopted as the initial condition, and the temperature / humidity control device is stopped and removed after setting the room for decontamination as the temperature / humidity condition A method for determining decontamination conditions, characterized by starting a dye test.